Well, sure, there were others that "had a role" in the disaster, just like there are passengers who would "have a role" in a bus flying off the overpass... but there's only one driver.
Who was this single bus driver? Was it the "independent" ratings agencies that were bought off by the companies that paid them to rate their products? Was it the money management firms (my field) that knew the ratings were a joke but where some people ignored them because of the fees they could generate? Was it the mortgage brokers that encouraged the liar loans? Was it the quasi-governmental Fannie & Freddie that accepted these loans knowing that they had a government backstop? Was it the guys at AIG that priced credit default swaps like it was car accident risk (claims occur mostly randomly, and costs are well understood) rather than hurricane risk (claims are all tied to a single event--the hurricane, and upper bounds of damages not easy to estimate).
I won't say anything more about this topic, because it's unrelated to gifted education, except this: If the Wall Street ratings firms were giving fraudulent ratings to Wall Street investment products made of loans issued by quasi-governmental Wall Street companies (who, by the way, were actually late-comers to the subprime party, which is always a surprise given how much primary blame they get, at their peak Countrywide owned 20% of the mortgage market, mostly junk) backstopped by a government with an incestuous relationship to Wall Street, then it isn't too hard to identify the driver.
Or maybe we're just dealing with a difference of terminology, because I consider Countrywide and Fannie Mae to be part of Wall Street, even though they weren't headquartered in New York (at the time under discussion, both were listed on the NYSE), so let's just say Big Finance instead.
