1. Mt 27:52-53 as literal fulfillment of Eze 37:12-14
It can be immediately seen that the passage in question fulfills literally this promise that the LORD made to Israel through prophet Ezekiel:
Therefore prophesy and say to them, ‘Thus says the Lord GOD, “Behold,
I will open your graves and cause you to come up out of your graves,
My people; and I will bring you into the land of Israel. Then you will
know that I am the LORD, when I have opened your graves and caused you
to come up out of your graves, My people. I will put My Spirit within
you and you will come to life, and I will place you on your own land.
Then you will know that I, the LORD, have spoken and done it,”
declares the LORD.’ (Eze 37:12-14).
I will highlight the exact correlation between the two passages by placing each action promised by the LORD through Ezequiel, in its two statements, next to its fulfillment recorded by Matthew:
Behold, I will open your graves / when I have opened your graves
The tombs were opened, and many bodies of the saints who had fallen asleep were raised;
and cause you to come up out of your graves, My people; / and [I have]
caused you to come up out of your graves, My people.
and coming out of the tombs after His resurrection
and I will bring you into the land of Israel. / and I will place you
on your own land.
they entered the holy city and appeared to many.
Actually, I think that Matthew did not state that this event was fulfillment of a prophecy in the Old Testament, as he did in many other passages of his Gospel, because the correlation between these two passages was so precise, so clear, so evident, that he thought it was not even necessary to point it out. Since he was writing for people familiar with the Hebrew Scriptures, his readers would notice the correlation immediately by themselves.
We should note that this physical fulfillment of the prophecy in Eze 37:12-14 is a sign of its way more important spiritual fulfillment in all Christian faithful. In other words, this multiple resurrection to physical mortal life was, just as Lazarus' resurrection to physical mortal life, a sign of the spiritual resurrection to eternal life which Jesus earned for us with His death and resurrection, which we receive when we are united to His death and resurrection in baptism (Rom 6:3-5), and which will result, at Christ's glorious return, in our resurrection to physical immortal life.
2. Mt 27:52-53 as undoing of Mt 2:16-17
Considering the following data:
a. "For this reason the Son of God was revealed, so that He might undo the works of the devil." (1 Jn 3:8).
b. Matthew is the only Evangelist who recorded the fact that king Herod "the Great" sent men to "put to death all the boys in Bethlehem and in all its vicinity from two years old and under," (Mt 2:16) after the visit of the Magi.
c. This fact, together with many others narrated by historian Josephus, shows clearly that Herod was a man to whom these words of Jesus applied fully: "You are of your father the devil, and you want to do the desires of your father. He was a murderer from the beginning," (Jn 8:44).
and looking in parallel at the narrations - exclusive to Matthew - of these two events that happened at the beginning and the end of Jesus' life respectively:
we can perceive an additional logic in Matthew's inclusion of both events in his Gospel: while Jesus' birth gave occasion for Herod to - as a reaction against this event - put innocent children to physical death, Jesus' death in filial obedience to the Father - which was his full manifestation as Son of God, according to his words: «When you have lifted up the Son of Man, then you will know that I Am, and that I do nothing from Myself, but as the Father taught Me, I speak these things. And He who sent Me is with Me; He has not left Me alone, for I always do the things that are pleasing to Him.» (Jn 8:28-29) - gave occasion for Him to - as a fruit of this event - bring back to physical temporal life people who, spiritually, were innocent (which is clear from their description as "saints" by Matthew), as a sign of the superabundance of spiritual eternal life available to all men thanks to his merits in his obedience to the Father to the point of death, even death on a cross (Rom 5:19 and Phil 2:8). In other words, this undoing of the privation of physical temporal life of perhaps a few dozen was a sign of the undoing of the privation of spiritual eternal life of perhaps thousands of millions.
(*) Let us note that this undoing a work of the devil was performed by the Son of God through the human nature that He had assumed, since it was Jesus Who, on arriving in the state of disembodied soul to the Limbo of the Fathers or Abraham's Bosom, ordered these saints who were there awaiting the Redemption to rise from the dead.
3. Mt 27:52-53 as literal fulfillment of Jer 31:16-17 if the raised saints were the children killed in Mt 2:16
I present now the hypothesis that the saints raised in Mt 27:52 were precisely the children murdered in Mt 2:16, so that Jesus, on the occasion and as a fruit of his death, undid the specific work of the devil done by Herod on the occasion of, and motivated by, Jesus' birth.
The first and foremost consequence of this hypothesis is that the resurrection of Mt 27:52 is the literal fulfillment of the prophecy of Jeremiah which follows immediately that quoted in Mt 2:18 as being fulfilled by the Massacre of the Innocents and refers to the very same subjects, the whole passage being (Jer 31:15-17):
15 Thus says the LORD, “A voice is heard in Ramah, lamentation and
bitter weeping. Rachel is weeping for her children; she refuses to be
comforted for her children, because they are no more.”
16 Thus says the LORD, “Restrain your voice from weeping and your eyes
from tears, for your work will be rewarded, declares the LORD, and
they will return from the land of the enemy.
17 There is hope for your future, declares the LORD, and your children
will return to their own territory."
It is also my view that, just as in the case of Eze 37:12-14, Matthew did not state that this event was the fulfillment of Jer 31:16-17 because the correlation between these two passages was so precise, so clear, so evident, that he thought it was not even necessary to point it out to people familiar with the Hebrew Scriptures, as they would notice the correlation immediately by themselves. (To the best of my knowledge, the only contemporary scholar who has interpreted Jer 31:16-17 as predicting, in the context of Mt 2:16-18, the resurrection of the slaughtered children is Professor Amy-Jill Levine .)
In addition, this hypothesis:
a. is fully compatible with the universal liturgical practice since the V century of commemorating the Holy Innocents, because commemorating them as saints implies to believe that they are enjoying the beatific vision, not that they were taken to the beatific vision right after Jesus' death together with Moses, the prophets, and all the rigtheous that were awaiting the Redemption in the Limbo of the Fathers or Abraham's Bosom. They could have arrived to the beatific vision through a holy life on earth. Let us note that leading these people to the beatific vision through a holy and spiritually fruitful life on earth procures more glory to God (epistemic glory = manifestation of his ontic glory) than taking them directly to the beatific vision.
b. explains the term "the Holy City" in Mt 27:53, which, if understood as referring to physical Jerusalem, would carry a strong cognitive dissonance. Would precisely Matthew, who a few chapters before had quoted Jesus saying "Jerusalem, Jerusalem, who kills the prophets and stones those who are sent to her!" (Mt 23:37) and a few verses before had narrated that "All the people answered, “His blood be on us and on our children!”" (Mt 27:25), refer to Jerusalem as "the Holy City"??? It is far more plausible that Matthew is referring here to the New Jerusalem, the spiritual Jerusalem, the Church: the raised saints appeared, or better said manifested, disclosed, revealed themselves as resurrected (*), to members of the Church.
c. explains the total absence of social impact in Jerusalem out of that resurrection of "many" (around 20 in this hypothesis) saints, since given that they had died 35 years ago while being less than 2 years old, and that they had been raised as adults, any inhabitant of Jerusalem that crossed ways with one of them would have no idea at all of whom he was, even less of the fact that he had been raised from the dead, and would simply take him as just another Jew that had come from far away to Jerusalem for the Passover. Only those members of the Church to whom these raised saints manifested, disclosed, revealed themselves as such, i.e. as resurrected (*), could come to know what had really happened.
(*) The word in Mt 27:53 usually translated as "appeared" is enephanisthēsan, 3rd person plural of the aorist indicative passive tense of the verb emphanizō, which appears 10 times in the NT, with the following meanings in the other passages:
Jn 14:21-22: manifest, disclose, reveal (oneself)
Act 23:15: give notice, make a report, notify
Act 23:22: report, notify
Act 24:1; 25:2; 25:15: present (a case against X), inform (Y about X)
Heb 9:24: appear
Heb 11:14: make manifest, make it clear
From these occurrences, it is clear that the expression in Mt 27:53 can be plausibly understood as meaning that the raised saints manifested, disclosed, revealed themselves as resurrected to many, that they notified many about their resurrection.
It is also clear that these "many" to whom the raised saints manifested themselves as such were exclusively members of the initial community of disciples of Jesus, because they were the only ones who could believe their testimony. Just think of the reaction of an inhabitant of Jerusalem in 30 AD (or of anyone in any place at any time) if a stranger approaches him saying: "Hi, I have been dead for the last 35 years and have just been raised from the dead. Would you be so kind as to provide me with lodging and food for a while?"
 Amy-Jill Levine (2019). "The Jewish Origins of the Christmas Story". TheTorah.com.