This is precisely what makes the movie the Big Short interesting: we see that people did identify, within a reasonable time frame, when people would start defaulting and how that would cascade into a true crisis.
It's pretty clear that while the fruits of AI are quite useful, the entire thing is rife with very questionable financial engineering... but I still don't know what it is that makes all of this break. For example, it's obvious that the SpaceX IPO is a massive wealth transfer program, but it's not obvious that it will immediately end in a crash. Given how irrational the stock market has been, I don't see a reason it can't continue to be irrational for long after the bag has been handed over to the retail investors and retirement funds.