Banking stocks can be pretty risky because of how complicated their businesses are. They don't merely take deposits and make loans anymore. They have very convoluted trading operations and deal heavily in derivatives. During the financial meltdown in 2008, many banks disappeared because the actions they were taking were so risky, and the banks that didn't go under suffered monstrous losses. Because of how interconnected they are, there weren't many banks that escaped unscathed. Banking is definitely one industry I am not interested in as an investor. If you want stable dividends, REITs are far more predictable and far safer, plus their tax structure necessitates paying out 90% of their income in dividends in order to maintain a tax advantaged status.
Yes, sorry, I did overgeneralize a bit too much. However, events like the 2008 crash are few and far between, and if you really pay attention, can be foreseen. While the crash was fairly sudden, the build up happened over time; something had to give eventually. Also, from the POV of a Canadian, our banks were fine
Events like 2008, specifically, may be fairly uncommon, but banking scandals are actually quite common. The 1980s was mired by the Savings and Loan scandal that wiped out over 1000 banks. Even currently, some of the largest banks in the world are dealing with scandals. Wells Fargo was caught creating millions of fake accounts under their customers names and then billing fees to the customers without their knowledge. Bank of America is still dealing with the adverse effects of their misconduct during the great recession. Deutsche Bank has been teetering on the edge of insolvency related to their own scandal, and will need to raise capital in order to stay in business.
As for seeing it coming, there were a few who saw it coming and took large short positions (at phenomenal risk) to eventually profit off of the collapse. But they were largely dealing in theories of what should happen based on information they had or theorized should be. It was incredibly speculative. Because of how opaque bank dealings are, the case for saying that people can see a collapse coming if they are paying attention is incredibly thin.
Canada and Australia are two notable exceptions to banks getting hammered by the great recession. But both those countries have much stronger banking regulations. The US, unfortunately, lags in this critical area.