There’s an article in the Atlantic – https://www.theatlantic.com/magazine/archive/2017/06/when-your-child-is-a-psychopath/524502/ – that also talks about this.
How people become cold and cruel. This is one of many reasons why we shouldn’t have wars any longer.
I also have a theory about the endocrine system having something to do with it. A constant high level of stress hormones is very unhealthy, so when that happens, the endocrine system starts changing some of its responses. (There’s research that supports this idea, yes.) That’s how cruelty can become associated with feelings of excitement and perhaps even of joy, except that it’s just the effect of a protective response from the endocrine system. Children have no way of knowing and controlling that.
It’s different for adults who become exposed to a lot of cruelty, but even for them, it’s hard.
