[he] built a net worth that's in the billions
could he do the same thing today if he was starting from scratch? Make a rather crappy [D]OS for the [at the time] biggest player in the industry [IBM]? Then perform a "IBM gamble" and become a monopoly? Benefit from being underestimated at the time from competition (Sun, Apple, HP) stubbornly keeping selling overpriced hard/software? Doubt that.
Memory fault -- brain fried