"But there were billions to trillions of dollars in fake wealth that turned out never to have existed" That is not true. They were financial assets which only have the value that people put into them. They are underpinned by confidence. Confidence goes away, it takes value with it.

"no serious attempt was made to figure out who exactly was screwing up" Exactly. Some very powerful people got very rich and it was in now bodies incentives to find anybody accountable.

These are interesting and may help you understand: https://en.wikipedia.org/wiki/Minsky_moment

https://www.sonyclassics.com/insidejob/