There’s nothing inherently wrong with mortgage-backed securities (they exist today!). In fact, there’s a lot right with them - they allow specialization by firms within the mortgage process and participation by investors with various risk profiles. It’s applying the Unix mindset of specialized composable functions to mortgages.

The 2008 crisis happened because MBSs became a bubble - investors stopped performing diligence (and risk models were crappy), so securitizers started packaging up crap, underwriting standards dropped, etc.

If you're familiar with the market and the dogma at the time, the idea was that securitization used mathematical techniques to actually reduce risk, and these were being sold as such. What's wrong was after this bubble popped, the taxpayer was on the hook for the socialized bailout, while the temporary profits were privatized. As such, while people like Fink may not have seen this through from start to finish, their ignorance or unwillingness to blow the whistle on something as destructive as this calls into question--in my opinion--their competence or earnestness in indicting others to effectively do what he should have done.

While there were definitely a bunch of shady things going on (e.g. Paulson helping Goldman negotiate a 100% payout of AIGs CDS obligations) during the crisis, the treasury actually made a profit of $15.3bn on TARP.