I’ve watched movies on and read about countless serial killers. Almost always they came from horrible families, with abuse, neglect, different types of punishment. Also it seems there never is any type of psychological follow up of them as kids when they started to act “weird”. So most are just forgotten people who were never looked at mentally. At least I the 70s, I don’t know today.

I think there a couple cases where that’s not true but rare exceptions.