That's overly simplistic. CDOs aren't inherently bad by themselves, and there are multiple types with a variety of underlying assets. It was the failure of the rating agencies to assess risk appropriately that made it into a crisis. There's been no proof of collusion among the banks to create a crisis, no specific people that criminal charges could be brought against, unlike in the case of VW.
By saying CDOs I meant their ratings. And while, as always, nothing can be proven on Wall Street, you won't tell me that giving mortgages to unemployed people and then selling it as CDOs (or even CDOs squared!) is good.
I made no claims to good or bad, of course the crash wasn't good, but the chain of proof isn't there for the financial crisis in the same way. I'm simply talking about provable fraud that needed to take place up the chain at VW, which, when you're talking about an engineered machine with clear trails of who's done what and multiple decision points over iterations of industrial components, it's much easier to follow to the source and prosecute accordingly.