Although I do agree their is no correlation between money and intelligence it did require some type of intelligence to take advantage of the opportunities that were presented him in order to make that money. Especially when Dana and the UFC were against him the entire time.
Theres also plenty of smart people throughout history that couldn’t speak for shit. You also admitted he was a good fighter, doesn’t that require some level of intelligence as well, physicality only takes you so far in the sport, even back then.