That's not what the literature says about differences in income - there, skills are indeed very relevant (though of course sheer luck and superstar dynamics matter a lot at the very high end). Wealth is a whole other ballgame, it's a stock not a flow; it grows globally when asset values rise (as they clearly have in recent times, due to r < g); and at an individual and subcultural level when people refrain from drawing down on it, preserving a long time horizon often across many generations.