I think its pretty naive to thing that it'd work this way. It's really bad idea. If someone has company that debuts on stock market, and stock price increases let's say 100x times, who is he funneling the funds from? I'd say it's not funneling but creation of wealth, economy is not zero-sum game.
If someone has a company doing an IPO, it’s extremely unlikely that the company was so small that one person did all the work. Why is it a given that one person should retain nearly all of the proceeds of the sale? To answer your question, that person is funneling funds from investors who are expecting returns derived from the labor provided by the undercompensated employees.
US had tax brackets in the 90%s for decades. It was part of a golden era for workers, for that and a variety of other reasons like strong unions.
Of course the rich tried to work around it. But culturally they also understood that paying a lot of taxes was considered their duty to society, especially in times of crisis.