I’ve had the thought that Hell being the absence of God results in the soul yearning for God’s presence and that it is this yearning which creates the real “fire” and torment in the soul knowing that God’s presence is forever denied.
They don’t “rest in peace” as those who were saved and repented before their bodies died.
However, they do have or retain a love of God that prevents them from belonging to Satan or to hell.
Therefore, they rest in purgatory after their bodies die, burning for Christ in the purifying suffering of their unrequited love and longing for Him until the final judgment.
I’ve read that those in hell truly wanted nothing to do with God in life, which is why they followed Satan.
So, naturally, they feel the same way in death as they did when they were in body.
Just speculation, of course.