A very wise author once said that a writer writes for himself, and then publishes for money. I write for myself and publish just for the reader.
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.