Alexander Acosta the US attorney who let off Jeff Epstein reportedly did so because he was told Epstein "belonged to intelligence". Turns out Epstein was an FBI informant.
https://technofog.substack.com/p/confirmed-jeffrey-epsteins-...
Or there was that time the FBI found links between the 9/11 hijackers and Saudi government. Which they promptly covered up.
https://archive.is/20230115173049/https://www.nytimes.com/20...