People like Ballmer did not become billionaires because they are stupid.
Most billionaires got that way though hard work, incredible ambition and even more incredible luck.
Mike
Or they were born on third base and thought they hit a triple.
That would be the 'even more incredible luck' part.
Conflating wealth with intelligence is a bad thing to do (see: Trump, Donald) but most people don't increase their personal wealth by any meaningful percentage without having some measure of ambition and drive.
Sure, there's no perfect correlation, but you can certainly say that smarter people, in general, have better life outcomes than the less intelligent, and that includes wealth, among other measures.