WaMu was shoveling money into "subprime" loans long after it was clear to sentient people that the housing bust was happening, or that at the very least the days of perpetual appreciation were over.
I put subprime in quotes because subprime loans are about the quality of the borrower (credit score) and this data was based on loan terms. Sounds like they were trying to save themselves by giving out a lot of loans with really shitty terms.