A lot of prisoners get released after about half their sentence when they become eligible for parole, so 12 years is really 6 (and life is really 20) in a lot of cases. Fraud is a white collar crime and basically everyone gets out on parole first or second try.
The only ones who don't are murderers, gang members, drug dealers or whistleblowers. The American legal system judges crimes on how far from "normal behavior" they are, not how much harm they cause.