It is clear that anyone who committed fraud should be prosecuted. What is not so clear is that the majority of these mortgages were to those who were "pressured, tricked, defrauded, deceived, or otherwise victimized". This is what your article and the Attorney General would have us believe but is completely unsupported. There was fraud but it is a fiction to suppose that the majority of Americans - while making the largest economic decision they will ever make - did not know what they were doing.
What is clear is that the decision to vastly increase the Government's (Fannie/Freddie/FHA) portfolio of sub-prime mortgages and the subsequent modifications to their lending guidelines (which the banks all followed) channeled money to people who never would have qualified under any sensible lending criteria. That decision was not fraud, just ill-conceived and politically motivated. But it is where it all started. (Hint: Google Andrew Cuomo HUD and Sub-prime) Greenspan didn't help but Andy, Barney, Maxine and Chris had more to do with it.
Is it cynical to question whether an Attorney General in the Administration of one of the perpetrators is chasing easy targets to direct us away from those who actually were involved?
It is also unclear why everyone who is "underwater" needs to be saved.
A fable: Two guys with the same income buy homes for exactly the same amount of money. Mr. A has saved up 25% of the purchase price and makes that as a down payment. Mr. B has no savings and takes out a mortgage for the entire purchase price. The value of both homes goes down 20% Mr A is not underwater; he just lost most of his equity and savings. Mr. B is underwater and has lost exactly nothing. But the Attorney General's, your article's and the Administration's plans all help Mr. B. The moral appears to be that saving and prudent purchase are not rewarded while overspending is.
So, investigate to find the cause. Knowing what happened will go a long way to avoiding a repeat performance, punishing fraud, identifying corrective measures, and making for better policy in the future (maybe). The easy target is just not always the right one to aim at.