The problem is that you're not just exposing one or two bad apples. It's like not one guy or his team did some shady shit. It's a major financial institution that a lot of people of all different levels of society have an investment in.
Sadly, this country would have ended up much much worse if we had held everyone responsible when shit hit the fan.
Every single major business in the US relies on a credit line provided by a bank, sometimes multiple banks. If you prosecute each and everyone who is responsible for the collapse you would find out that the problem is systemic and in turn would have to shut down almost all the major banks. Thus eliminating the world credit line. You would literally stop the world economy in one fell swoop.
The right approach would have been to implement stricter reforms and regulatory oversight. Neither happened so we are still vulnerable.