I think it's a personality trait. He actually enjoys talking to dozens of people every day. He's friends with pretty much all the professors at the local uni because he turned up to random events as a student, and somehow he met a director level person at my company at the dry cleaners and they have regular catch-ups. he keeps a notebook of small facts about everybody in his network. COVID lockdowns were devastating for him.

In contrast, my Dunbar number is about 5. I need a few days to calm down from meeting new people. I can't imagine putting in the effort that he does in collecting people. COVID lockdown was a welcome break for me.