Here's the one lesson I really want us to all learn from this: the only thing the rich fear is prison because prison robs them of time. Fines are just the cost of doing business. There are many other scandals: the whole subprime disaster, pollution from plants and the like where no one went to prison and people really should've.
Unfortunately, the highest levels of financial crime are tied to lawmakers and corruption of the highest authorities of white collar law enforcement.
It's usually outsiders and smaller operations that get caught. Corporations are in charge of a corporate oligarchy, which is the United States.
These entities are "too big to fail". They are so essential to the economy that the best you can hope for from the government is maybe a scapegoat going to a comfortable prison or a hefty fine.
TL;DR
Bringing down the largest corporations for crime is like trying to arrest the US president for war crimes.