https://fas.org/man/eprint/contract-fraud.pdf

Highlights: from 2013-2017, there were 1,059 criminal convictions of defense contracting fraud (1087 defendants total), including 678 individuals and 409 separate businesses. Further, there were 443 fraud-related civil cases.

These are just the ones who got caught. It's not that much of a stretch to think that this much money is going to be super tempting to well-connected cronies of our representatives.