The tax scheme being over 90% didn't mean anyone paid that.
You should look at the share of GDP that different tax rates bring in. Marginal tax rates have no relationship to increased tax receipts. Full stop. That's a myth propagated by fake progressive politicians who either don't know better or (more likely) do know it and use it to raise campaign funds.
All a high income tax does is to incentivize different forms of compensation. Rich people have the top CPAs who dunk on the CPAs who work or the IRS. It's not a matter of simply raising taxes, because it's not a binary system. It's immensely complex and dynamic, and in the end, every tax that was first levied against the 1% ends up being paid by the 50%, like myself. On behalf of myself, please reconsider your tax policy. I don't have the means to hire the best CPAs so your ideas only hurt me, eventually.
For the answer of why there are so many more billionaires, consider the cantillon effect coupled with wtfhappenedin1971.com