Why does the stock market function and who runs it?

The creation of stock market is for the companies to raise money. That’s fine. But SEBI does allow the brokerages to give leverages to their customers that means some big guy wants the stock market to run and function… He would want the market to function and run only if he is making money out of it. Who is that BIG Guy and How does he make money?

A follow up question - If more than 95% of the volume comes from big investors (not retail traders) and considering the Stock market as the zero sum game… From whom are these big investors making money from? From other Big investors or retail traders?

brokers give leverage because that helps them generate more revenue not because some big guy wants it… everyone is here for the money right from smallest trader to regulators who keep everything in line…

they might be making money from any participant in the market… doesn’t necessarily has to be other big investor, it can be plenty of small investors as well…