People are fascinated by evil because it's mysterious and it doesn't seem to have a rationale behind it, and the second you say that Hannibal Lector was abducted as a child and he had to eat his sister or something like that, it becomes immediately mundane. The character becomes mundane.
“I know that I have lived because I have felt, and, feeling giving me the knowledge of my existence, I know likewise that I shall exist no more when I shall have ceased to feel.”