The CIRA was really a very small part of the problem. What really drove this was the massive number of previously creditworthy people defaulting on mortgages due to a combination of two things: (1) poor decisions about buying homes at inflated prices, and (2) job losses in the 2008-2010 period.
Goes back even farther Johnson’s Great Society programs
Why were there so many job losses during that period?
Plus the inflated ratings mortgage bonds got from crooked services like Moody’s and S&P that valued pure junk at BB and even A levels. So funds were trading securities for millions of dollars that weren’t worth anything. When the first card was pulled out, the whole house collapsed.