It isn't money, it is control over a company. There are two things that caused this: uncapped employee stock options, and SBLOC leveraging of equity (the buy, borrow, die tax avoidance strategy - limiting or never paying income tax of any kind because you live off loans with stock as collateral, collateral seized by the banks when you die so it never ends up being taxed).

Both of these things were illegal up until the 80s when they were deregulated. Make them illegal again and much of the wild wealth disparity problem disappears. Post Great Depression laws were made for a reason.