The housing bubble and associated financial crisis was caused in part by a "homeownership for everyone" crusade, which necessitated lowering mortgage underwriting standards.
Wall Street played a role in the housing bubble and financial crisis, but so did politicians who pushed for easy credit, quasi-governmental entities such as Fannie Mae and Freddie Mac who purchased low-quality mortgages, off-Wall-Street mortgage brokers who encouraged people to borrow too much, and home buyers who borrowed too much and lied on their mortgage applications. Blaming Wall Street alone makes for a tidy morality play but is not accurate.
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.
First of all, there's almost no difference between Wall Street and the federal government anymore, because they all went to the same schools, they're constantly exchanging employees, and the latter owes its job entirely to the campaign financing of the former. So pretending they're different entities is a waste of time... they're both privileged members of the top 1% financially. This is not to be confused with the top 1% IQ... a Venn diagram of the two groups would look not unlike the view through poorly-focused binoculars.
Also, by "quasi-government entities," you mean, "private companies which enjoy a legislative guarantee to privatize their profits and socialize their losses."
By "off-Wall Street" you mean mortgage servicing firms, who were being doggedly pursued by Wall Street to produce more product, being paid lavishly by Wall Street to do so, and were assured that, since the mortgages were being sold upstream, the servicing companies would have no skin in the game.
Then these same Wall Street analysts who cooked up this pyramid scheme began repackaging loans, trading default options and buying insurance amongst themselves, while making absurd guarantees to their investors, buying favorable investment ratings that had no basis in reality, and overall creating such a fantastically elaborate fiction that they even started believing it themselves... because... talent?
