He's so ugly, you know he never got laid in high school or college. He's making up for lost time.
I think there is some truth to that R4, he isn't conventionally hot and has a weird name. Probably was always a big horn dog but never had much luck with the girls. Now that he has the prestige to get as much sexual attention as he wants he clearly can't help himself.
He's hypersexual (in other words, horny like a lot of straight men) and unfortunately took a decent but likely much less sexual woman as a mate. He was bound to seek release elsewhere.
I've seen this time and again, straight guy with big ambitions, in this case political, chooses a wife or partner based on practical reasons or for show. They are poorly matched emotionally/sexually, and trouble ensues at some point. This is just a highly public instance.
Why are there so many threads about him? Why are New Yorkers so obsessed?