My comment is a difficult idea to express, but if you’ll bear with me here:

Psychopathy strikes me as individuals born with a specific profile of traits that interacts with their environment during childhood to result in a preferred neurological pattern of brain development that then drives psychopathic behaviour in a highly compulsive way. I suspect other neurological profiles can and do result in other individuals born with the same grouping of traits. What I’m trying to articulate here is that the emergence of an evil adult person is the evolution of the darkest possible expression of people with those traits, but change the early environment, then you change the later adult expression. What I think is lacking is an in-depth understanding of what these children need to develop into better adults. They may be children that are highly vulnerable to environmental influences - more so than others.

The problem is that these individuals commit such horrific acts that they’re not evaluated without triggering revulsion in society. We may be failing to see their humanity by being blinded by the disturbing nature of the their compulsive violence (understandably so). More knowledge is needed.