Robert Reich's "Saving Capitalism" documentary on Netflix does a pretty good job to answer this question.

TLDR; Wall Street is part of an industrial/political system that extols "free market" capitalism, publicly, when in fact, "free markets" and "free market meritocracy" is a myth, and they know it. Privately, these same people hire lobbyists and otherwise influence the political system to craft regulation & policy around property, monopoly, contracts, bankruptcy, and enforcement. These regulations protect and enhance the benefit of the few.