The problem with just taxing it all away to prevent him from being a billionaire is the money is tied to control of the company, so it's equivalent to saying nobody can build a business bigger than some arbitrary limit. Which is equivalent to saying nobody can build a business with more than a certain arbitrary number of employees. Where would any of us work if that were the case? It's not at all a given that you would get millions of new small and medium businesses that would completely make up for that gap you'd have from lopping off every big company at a couple billion dollar market cap. The world is just not zero-sum like that as much as progressives might (either deceptively, or obliviously) pretend that it is.
> Paul would never fund a founder who wanted to divide all profits among employees
While YC might not recommend a founder take literally 0% equity, they are hugely supportive of founders giving more equity to employees and keeping less for themselves and have done a lot to move the industry in that direction https://blog.samaltman.com/employee-equity