I don't think anyone sat down and said, "I'm going to create a housing bubble, tank the economy, have people forced out of houses they couldn't afford because of said bubble, and cost millions of people (including myself, with high likelihood) their jobs".
Wall Street has had some very negative effects on the economy, but I don't think those were intended. There wasn't malice. It's just that we, as humans, are terrible at handling complexity beyond certain levels. Take one of those now-infamous mortgage-backed securities. To analyze the thing, you need an economist, a mathematician to model it, a programmer or two to write (and test!) the modelling code, business people who know the involved counterparties and how they will behave under distress-- that is, will our counterparty make good, or default?-- and lawyers (because the damn things are, at the end of the day, contracts). The things are dangerous because no single person on earth holds even half the knowledge to know what the thing is actually worth. But (as in government) that complexity is the product of creep, not (in most cases) intentional malice.
Wall Street people are ruthless and greedy. If the trade they want to do means getting up at 3:00 am (or, even, getting the team up) for the European open, they'll do it. They want to win, and they play hardball. However, Wall Street's rules are well-defined (unlike in VC) and most of the obviously unethical things have been made illegal. Wall Street people, for the most part, don't like being in jail and would rather avoid that. Most people on Wall Street are (although ruthless) actually ethical. There are exceptions but they tend to take a lot of collaboration (see: housing bubble) and it's actually hard to get people like that to "conspire" on anything. It just has to happen, emergently, and it only happens once every 10 years or so.
See, predictable, greedy, and mostly ethical people (with a few unethical ones in the mix, as anywhere) aren't that dangerous a set. If someone costs you your job, you get another one. No big deal. It's true that you have about a 20% per year chance of getting laid off on the street, but it's not stigmatized and your co-workers (and often your managers) will go to bat to help you get a better next job. (Silicon Valley probably has the same 20%/year job-loss rate, but startups refuse to have an honest lay off and mask those firings as "performance"-related or "cultured fit", meaning there's no severance and the startup's reputation is preserved at the expense of the ex-employee.)
In the Valley, people may not be as open about liking money, but they are more hung up on power and, at high levels, it's like high school. That's why social proof is so important in raising the first round of funding: because it's essentially adolescence all over again. The stakes are lower (Silicon Valley can't tank the economy in the way that Wall Street can) but the petty personal grudges are more common and people are much more willing to go out of their way just to hurt someone they dislike.
It used to be, in the Valley, that people went out of their way to help each other. If a startup CEO had to lay people off, he introduced the laid-off people to investors so they could start their own companies (presuming they didn't compete directly with him). Now, that same reputation economy exists but, instead of it being powered by people helping each other out, it's powered by people pushing each other down to solidify their own positions.
How confident are you about this claim?