Well never actually know. Dumbass gangsters said he was smart but that’s coming from dumbass gangsters.

A lot of his business successes can’t be attributed to being a smart business man because we don’t know to what extent being the boss of a crime family played in those successes.

I think Paul was probably a genius compared to other gangsters and very smart compared to the general public.

He was certainly smart enough to use his position to create wealth from it. As mentioned his lack of a relationship with the rank and file literally killed him.