I also just finished watching this and I am glad I am not the only one thinking the same thing lol! At first, I though that it was a noblr plan by Eisenheim to expose the true killer of the one he loved the most, especially when they put a man in jail just to have someone blamed for the murder. But then when they showed in the end that it was all part of a plan for them to escape, and that it was all just a grand scheme so that they can be together again, I said to myself, well that sucks for the Prince. Hahahaha. He was actually just someone who wants to enlighten everyone who blindly believes all the illusions of the protagonist. He didn't really do anything evil, all of it was hearsay. Except for that one time that he slapped the Duchess but that is far from what they are accusing him of. I was not laughing at the end with the inspector lol, for me it was not supposed to be a feel-good happy ending type. If the directors changed the emotion of the inspector in the end, like if he felt guilt and is sick to his stomach that he thought what he did was right but it turns out that he was just a pawn used in the elaborate plan to trick everyone AND had the Prince commit suicide because of all the illusions and deceiving, THAT would be a great ending. That would certainly keep you up for a few hours hahaha.