The genesis of most such financial problems is the emergent behavior of the complex economic system we have.
The behaviors - which were familiar scams transposed to modern opportunities - did not magically "emerge" until the key banking regulations were repealed, and enforcement of remaining law cut way back.
No one person caused the problem by buying homes they couldn't afford. While there was some nearly criminal activity (i.e. rapid flipping with no intent to ever live there or pay the mortgage) most people just took advantage of good mortgage rates. Likewise, while some fund manangers were frauds (i.e. selling packaged mortgages that they knew were astronomically risky) most were just trying to make money for their investors.
It was massive fraud - a bubble of epic scale, inflated by corruption and dishonesty. Deregulated and lawless greed. The normal and historically standard and easily predictable and in fact predicted behavior of unregulated moneylenders since Cain invented money.
Even at the level of the retail mortgage, the trivial aspect, the individual borrower buying a house to live in, the straw that broke the camel, there was massive fraud; Countrywide, for example, was iirc the biggest household mortgage lender in the US - coast to coast operations. It wasn't just "some", but the biggest and market setting players, the central and dominant insurance operations, the ratings agencies with 90% of the business.
The larger part of the real estate lending fraud and collapse was in commercial real estate.
And the fraud bubble in the derivatives was twenty or thirty times as large as the retail wing entire - ten times as large as the entire US housing market including the loans that were solid and legitimately financed.
Nor was the problem evil corporations intending to take grandma's house, or a cabal of flippers intent on damaging the economy.
They didn't want grandma's house, and they weren't intent on damaging the economy, of course not. Why would they care? Like all unregulated moneylenders and market players from time immemorial, they were intent on defrauding the public and each other, raking in boatloads of profit from corrupt and manipulative dealings with any victims they could pull in, winning and growing rich. Even short term consequences were somebody else's problem - the health of the economy was a matter of complete indifference to them; being rich, they assumed they were immune from economic disease.
And that assumption was borne out, for the most part. They are still rich. They are not in jail, but in power - sitting in Trump's administration, consulting with Congress, schmoozing at Davos. They got to keep the money, for the most part. Afaik not a single one was rendered homeless. No more than a couple were jailed. Even the few who suffered the indignity of being deposed under oath, fined, and excluded from polite company, are living comfortable lives of luxury:
https://en.wikipedia.org/wiki/Angelo_Mozilo