No, not to a person. There can be some stupendously dumb billionaires, especially since inheritance is a thing. I would however expect the average intelligence however-measured of the 100 richest "self-made" (lets just say who didn't themself inherit a generational amount of wealth) individuals in the US to be higher than a 100-person random sample of the population.

Equating achievement to financial success is a big mistake, but a bigly American one. The great scientists, while often somewhat privileged, were rarely in the billionaire class or their time’s equivalent. The average brilliant scientist or mathematician nowadays is making a wage that doesn’t afford them any luxuries whatsoever.