I'm not sure what your point is. Nothing you say disagrees with my point. The credit crisis was multi-faceted, but poisoning of AAA securities with subprime was definitely one of the major fraudulent aspects of the entire thing.

AAA doesn't mean that the security will pay out. It means they have the lowest risk and it means that it's the most expensive. Even AAA-rated debt can fail.

What happened was that large financial institutions were paying top dollar for AAA mortgage-backed securities, but after it was revealed that all of these mortgage-backed securities were poisoned with subprime loans, the value of those securities plummeted. The value of those assets dropped, which put the holders of those assets in a bad financial situation because they didn't have as much money as they thought and they also couldn't sell them. Some companies or funds are legally required to hold only AAA securities. This caused reverberations throughout the financial industry.