Pure ideology. The right thing to point out here is that capitalists have a lot of material advantages that go way beyond the liquid balance in their bank account. The ability to access easy, virtually unlimited credit is probably the most relevant here. If we seized all of Elon Musk's liquid assets ( ), he probably would be a centimillionaire again pretty quickly, because there are tons of entities--both institutional and individual--who would be more than happy to hand him free money because of who he is. If people are willing to hand you millions of dollars for free, give you preferential treatment as an investor, and generally bend over backwards to ingratiate themselves to you, it's almost impossible not to end up super rich.

This is part of why "taxing the rich" is a bullshit lib non-solution to the ghoulish system we have now. The problems are structural, and a small number of people have privileged virtually unlimited access to the means of production. If you took away that access, most billionaires would fare significantly worse than ordinary people, because they don't actually have any skills beyond exploiting their privileged access to capital.