Ah yes. Looking more closely at the save, I noticed that your liege, the Basileus of Byzantine Empire, is a Catholic. Being the good Catholic he is, he will give back Rome to the Pope. So the behavior is WAD.
However, the game doesn't really say anything about why that happens, though. I'll make sure that we look into giving the player better feedback for when this happens.
However, the game doesn't really say anything about why that happens, though. I'll make sure that we look into giving the player better feedback for when this happens.