[C4stor]

You possibly vastly underestimate how important it is for people commiting "perfect" crimes to tell the world it was them. There's a lot of stories about forgers including subtle clues in their forgeries to be able to claim their "art" and prove they duped people.

[keerthiko]

This. This is also essentially the premise for (the original) Death Note (except a God complex rather than proving they pulled a fast one).