Well, you don't have to be a financial expert to understand the generalities of what you can and cannot afford.
The rest of what you describe can be equally attributed to greedy people thinking, "if the price doesn't rise, I'll bail in 3 months. No loss." I know some of those people.
>But if you think it's a precise 50/50 split or anything close to that, I think you are a terrible judge of the situation.
I know you read stories about the strawberry picker who can't speak english "pressured" into buying the million dollar home, but those cases were extremely rare.
The majority were people with $40,000 in income deciding to buy the $750,000 house, rather than the $200,000 house, because, you know, the American Dream says renting is bad and looking wealthy is a necessity. Give me the most money you can for the biggest house possible! This happened across the globe.
Oh, and you're forgetting the other major factor of the American specific bust: people who used their home equity to fund consumption. Mostly boomers. I guess those were also the unfortunate, duped poor, buying vacation homes, jet-skis and third cars?
It seems that your understanding of the situation is drawn from the mainstream, "evil-bankster" meme. But that only works because it's a populist sentiment. There is plenty of blame to go around; give it to the greedy.