>> I honestly have not a single idea why there wasn't this type of department before monitoring and auditing everything.

You mean like the Government Accountability Office? [1] Or the dozens of Inspector Generals at most agencies? [2]

[1] https://www.gao.gov/

[2] https://www.oversight.gov/where-report-fraud-waste-abuse-or-...

The US federal government has lots of laws, agencies, and procedures to address, investigate, and remediate fraud, waste, and abuse.