Revelation 20:7 Now when the thousand years have expired, Satan will be released from his prison.

Every time I read this my first question is always, “Why?”
I do not claim to know God’s purpose in releasing Satan but I can speculate.
First, it may be God’s holy righteousness to prove the judgment and condemnation of Satan.
He has a thousand years to meditate over his crimes against The Almighty and humanity.
We put people in prison in hopes of rehabilitating them back into society.
They should learn from their crimes and incarceration.
Just as it does not work for many hardened criminals, it does not work for Satan.
My second thought is a righteous judgment against humanity.
So many people say a loving God would not condemn anyone to hell.
After a thousand years of Christ ruling, many citizens of the planet rebel against Him through the deception and temptation of Satan.
They went up on the breadth of the earth and surrounded the camp of the saints and the beloved city (Revelation 20:9), whose number is as the sand of the sea (Revelation 20:8).
This brings another question: who are the rebels?
Are they believers? It was believers in God that rebelled in the days of Moses.
Are they survivors of the tribulation that need Jesus as Savior?
I don’t think there is a clear answer but given enough time, we’ll know the answer although that is at least one thousand years away!
Regardless, God’s response to the rebellion – fire came down from God out of heaven and devoured them. Revelation 20:9