It wasn’t necessarily obvious that specific banks would fail but it was obvious that the big guys were playing high-risk games and were going to be left with a lot of foreclosures or writing off a lot of paper value. This was known to basically everyone in the industry, too - I briefly considered buying in New Haven in 2008 and got mortgage pre-approvals from a few banks. I had an interesting conversation with an older loan officer at a Connecticut state bank, who was the only one who didn’t approve me for WAY more than I thought reasonable and explained why very matter of factly, and noted that since his bank didn’t resell the mortgages as CDOs they had to be more careful about risk.