The Washington Mutual-related mortgage securities,
were insured.
The ABS CERTS are Bonds and are insured by derivatives. The Trusts were insured. JPM was a major writer of the contracts covering the Bonds. So when;
"seeking to shift losses on over $190 billion of Washington Mutual-related mortgage securities onto the FDIC – claiming that for a mere $1.9 billion it bought nearly all of the positive value of WaMu and was able to stick the public with essentially all of the ongoing losses",
JPM was trying to avoid payment to cover the ABS losses. The crisis in 2008 wasn't the the mortgages, but the insurers inability to cover the mortgages loses. JPM didn't have the needed cash, and nor did the FDIC to cover JPM's losses.
Searched; causes of 2008 financial crisis "The financial crisis was primarily caused by deregulation in the financial industry. That permitted banks to engage in hedge fund trading with derivatives. Banks then demanded more mortgages to support the profitable sale of these derivatives. ... That created the financial crisis that led to the Great Recession."