I believe that my late father met the criteria for NPD and that it was largely environmentally caused. He had a difficult childhood but he DID love – himself, mostly.

All of us have a nature that may do well in a positive environment, not so well in a poor one, and some people are resilient no matter what the situation.

There’s an article on the main PC page about the differences between psychopaths and sociopaths which addresses nature/nurture in people with anti-social personality disorder.

Differences Between a Psychopath vs Sociopath | World of Psychology

To quote just one sentence: “Psychology researchers generally believe that psychopaths tends to be born — it’s likely a genetic predisposition — while sociopaths tend to be made by their environment.”

James Fallon does not have antisocial personality disorder. I’ve seen him in a video saying that he is narcissistic so I’ll take his word on that. But if some people with antisocial personality are made, not born, seems likely that the same would apply to people with NPD.

So far as I know, though, there's not a clear difference in terms for people with NPD who may have psychopathic brains and those who may not.