Incorrect risk management from investment bankers, treating highly-variant finance as deterministic physics, and a fanciness of extremely smart people to invent extremely complex solutions, which obfuscate the ever-increasing assumptions and are less robust to black swan events. This illusory superiority bias over the common man, giving too much authority and decision-making power to a set of mathematical functions, and a culture of financial optimism and realization that you are too big to fail. This is what caused the big crash of 2007-2008.
The common man, as a class, lost money from that crash. In response, Bitcoin and fractional stocks were introduced. New markets emerged, where wearing a suit or MBA seems a negative, not a value add. Now, as a class, you at least have the possibility to win money. Else you always lose (but maybe that's the natural way it is supposed to be, not everyone can be the queen ant, or has the adaptation capacity to become one). BTW: every hedge fund that opened their data to the public, saw better, more accurate, models being build on that, than any of their elite quants in-house was able to beat. The masses, when harnassed, are no match for even the biggest hedge funds.
Um, yes. Retail investors as a class lose money.
Remember, you're betting against people for whom this is their day job, work in a business that drops the losers, and have far more money than you.