The idea that he is just peacefully sleeping won’t leave me alone
But the things Hitler did live on and not just in history. The karmic consequences, which have nothing to do with God but everything to do with underlying spiritual laws of the universe, remain. His soul will have to go through much to cleanse and balance the atrocities he perpetrated.
My view of the karmic universe is that no one gets away with anything. And Hitler is no exception. Karma is a more accurate justice system than the criminal justice system ever was. That is because it operates out of universal principles and is not created or enforced by fallible humans.