I think you're conflating "people who work on Wall Street" with economists. Most of the "dirtiest" of the loan originators were people with no financial education whatsoever; salesmen, and nothing more.
>"If the Fed hadn't pumped easy credit, first during the dotcom bubble, then into the housing bubble, would the blowup have happened?"
Yes. Blowups happen. It's the business cycle. A credit driven economy inflates until marginal borrows default, which cascades to a deleveraging. The Fed "pumped" money in the economy after the dotcom bubble because we saw some of the greatest destruction of wealth, ever, during that period. And much of the housing portion was political mandate.
Admittedly, economics and the economy is a finicky patient. But contrary to popular belief, these guys are smart and know what they're doing.