I think the larger group is in the middle: People who didn't really know they might have trouble with this mortgage in the future. It seemed like a house purchase that made sense at the time, and then circumstances changed; or, they thought if they got in trouble they could sell the house, but surprisingly their house is now actually worth less than when they bought it, something a lot of people didn't realize was possible.

One big difference between homebuyers, as a group, and bankers, is that homebuyers aren't expected to know finances and markets to nearly the same extent, and are much more at risk of making what turn out to be bad decisions, completely in good faith.

I agree that your second group (bad thing happened) is much larger than your first group (people knowingly taking on bad risk), but I think my middle group is the largest.