If in the end it was the home owners who shouldn't have bought homes that caused the collapse, what could the likely regulation be? Seems to me ultimately it would be "people must be protected against themselves", that is, it would be a patronizing regulation that would assume that people in general are too stupid to take care for themselves. In turn, this would take away the capability for people to make decisions for themselves. In short, now maybe too many people owned homes, then too few people would own homes.
Personally I think that any regulation that pretends to know better what is good for people than the people themselves is flawed on principle.
What should of course be illegal (and probably already is) is fraud. Telling people they can afford something they can't afford could be fraud, to be decided on a case-by-case basis.
The really scandal to me is that they don't seem to teach anything at all about personal finances in school - at least in Germany they didn't. I guess it is just not a prerequisite or even counterproductive to making you a docile, useful worker.