In Trump's mind, and that of a considerable portion of Americans, wealth is equivalent to talent and ability. So, if you're poor, it's solely because you're untalented and/or unmotivated. Of course, viewing people that way, you wouldn't want poor people in your cabinet.
Anyone with sense knows that's total garbage, but that would require conceding America isn't the land of 'pull yourself up by your bootstraps' like the right-wing love to proclaim.
America's semi-secular version of the prosperity gospel is one of our worst traits.
Putting people in charge because they're rich is the equivalent of betting on a die to roll high because it rolled high last time, and besides, you like how it looks.