One of the drivers behind this is the tax preference for debt over dividends. There's been a trillion dollars worth of stock buybacks since 2008, an action taken mostly to reduce taxes. That generates work for Wall Street, and wealth for those "near the money", working on various deals.
Then there are "hedge funds". Hedge funds, as a class, underperform the market, partly because of their excessive fees. The traditional hedge fund fee is "2 and 20", or 2% of the amount invested each year plus 20% of gains. This, too, is self-generated activity of Wall Street.
Then there are Exchange Traded Funds. Regular mutual funds are priced once a day, after the market closes. ETFs are constantly traded, generating commissions. ETFs have some tax advantages over regular mutual funds, and are thus another exploit of a flaw in tax policy. They can also be shorted and optioned, which are zero-sum operations which do nothing for the economy.
Then there's high-frequency trading, which is a form of front-running. This skims a tiny percentage off of other transactions.
None of this contributes to capital formation, and most of it was illegal a few decades ago.