Everyone wants a villain: lefties want to hear that it was greedy bankers, or cold-hearted deregulators (or better yet, both!) who are entirely and 100% to blame; conservatives want to hear that it was poor people taking out loans they knew they couldn't pay off, and a pandering government that leaned on companies and the taxpayer to hand those irresponsible wretches free money.
Nature is not a novelist. Reality does not come packaged in narrative form, and rarely gifts us with either true heroes, or true villains.
It is safe to say that almost everyone involved in this mess, from the borrowers to the bankers, thought that they were getting away with something—at the very least, that they had found a way to get rich without working. It is an old saw that no one can be conned unless they are willing to believe in something for nothing, and the best cons generally get the victim to believe that he is putting one over on the con man.
It is trivial to observe that humans are imperfect; that is why institutions exist.
Read it here. Emphasis mine.
I would only add that institutions are created by humans, staffed and directed by humans, and therefore subject to all the frailties and foibles of humanity.