2 Peter 2:4' "cast them into Hell" doesn't use the Greek word that is normally translated as "Hell".
Instead it uses the word ταρταρόω (tartaroō), which is used nowhere else in the Bible, and obviously must mean something quite different from how the ESV (and other) translators wanted people to understand the term.
The Book of Revelation also tells of Satan's being cast down:
12:9: So the great dragon was cast out, that serpent of old, called the Devil and Satan, who deceives the whole world; he was cast to the earth, and his angels were cast out with him.
12:13: Now when the dragon saw that he had been cast to the earth, he persecuted the woman who gave birth to the male Child.
Similarly, Isaiah 14:12 (NIV) describes the fall:
How you have fallen from heaven, morning star, son of the dawn! You have been cast down to the earth, …
Notice that Satan was cast to the earth, not into some special place of perpetual torment.
Satan and his demons were simply banished from God's Heaven and confined to the physical Earth.
They could be explicitly summoned by God (as in the Book of Job), but of their own free will they were denied access.
After having access to God's Heaven since before the creation, being confined to Earth must have seemed like "chains of gloomy darkness".
Notice Satan's behaviour in Job 1:7:
And the LORD said to Satan, “From where do you come?” So Satan answered the LORD and said, “From going to and fro on the earth, and from walking back and forth on it.”
Satan is describing his life on Earth as if he is sarcastically describing it as pacing within a confined prison cell.
Being confined to Earth does not prevent Satan and his demons from entering into and possessing individual humans.
This would be part of how he "persecuted the woman" (God's Church) in Revelation.
Related: my answer to Why was the Devil/Satan not chained and kept in darkness like the other fallen angels mentioned in Jude 1:6 and 2 Peter 2:4? - Biblical Hermeneutics Stack Exchange