trading house

All;
I have been trading stocks for 4 years more or less (Mexican Stock Market. I do not think that (taking luck out of the equation) anyone can predict the price movement of a stock based on an average (or any variation of it) or high-low level or a so called "indicator" resulting from historical prices. That being said a question arose, How do the trading firms actually make money (Besides hedging, networking with several governments and being sort of a Market Makers meaning owing a position for some commodities)? Mercuria, Glencore, Mercuria, bunge, Vitol, etc despite having production, logistics and storage infrastructure, make a good part of their revenues from paper trading (trading with futures) thus no physical delivery occurs whatsoever. I really hope the missing part of the puzzle is NOT technical analysis hahahah..
Best Regards
GE