The promises made to Israel were conditional promises. He had plans for them if they obeyed and kept His Holy Commandments. The rest of the nations were supposed to see Israel and come to God through their example.
'Now then, if you will indeed obey My voice and keep My covenant, then
you shall be My own possession among all the peoples, for all the
earth is Mine; and you shall be to Me a kingdom of priests and a holy
Exodus 19:5, 6
Unfortunately, they did not obey, nor did they listen.
For they have not listened to my words,” declares the Lord, “words
that I sent to them again and again by my servants the prophets. And
you exiles have not listened either,” declares the Lord.
As in the Parable of the Tenants told by Jesus in Matthew 21:33-44 the privilege of being part of Abraham's true seed, the True Israel, the Kingdom of God was taken away from those who rejected it and given to those who accepted it, Jew or Gentile.
“Therefore I tell you that the kingdom of God will be taken away from
you and given to a people who will produce its fruit. 44 Anyone who
falls on this stone will be broken to pieces; anyone on whom it falls
will be crushed.”
Jesus was sent for the lost sheep of Israel.
"Do not go in the way of the Gentiles, and do not enter any city of
the Samaritans; but rather go to the lost sheep of the house of
Matthew 10:5, 6
Nevertheless, at the stoning of Stephen, he made one final appeal to the Israelites:
“You stiff-necked people! Your hearts and ears are still
uncircumcised. You are just like your ancestors: You always resist the
Holy Spirit! Was there ever a prophet your ancestors did not
persecute? They even killed those who predicted the coming of the
Righteous One. And now you have betrayed and murdered him— you who
have received the law that was given through angels but have not
And so the gospel went to everyone, and not only the Jew. If we love God, believe in Christ, and obey His Holy Law, as the Israelites of old failed to do, we ARE Abraham's seed. These promises that were made to Israel were conditional promises, and they still are!
According to Paul, we, as modern day Christians are the true Israelites. This is because
if you belong to Christ, then you are Abraham's seed, and heirs
according to the promise.
Now, the kingdom of priests and the holy nation are not physical Israel, but Spiritual Israel, who are those who believe on Jesus and keep His Holy Law.
But you are a chosen people, a royal priesthood, a holy nation, God's
special possession, that you may declare the praises of him who called
you out of darkness into his wonderful light.
1 Peter 2:9
These promises can be claimed by those who are in Christ.