Idk on one hand I can't understand it at all but on the other hand from my reading around the subject since then, I think what motivates them are some of the motivations we might have too, like a desire to feel special, a desire to experience a thrill, a desire to have power and agency in our lives.

Only with them the channels they choose to achieve it are different and their lack of empathy puts a lot of options on the table for them that are just unthinkable to us.

After my run in with that guy I read up on APD and con artists so I would be able to spot it sooner in future. There are plenty of people with APD who don't choose to nurture that side of themselves.