That cocksucking, weirdo, tranny pervert Gay Edgar Hoover was obsessed with good publicity for the FBI. The crew cuts and suits, the recruitment of Mormons, the relationship with Hollywood and the Press. Hoover spent most of his time handling PR (and political blackmail.)

The FBI was founded as the domestic secret political police of the (((Deep State))) and was just as crooked and evil back then as it is now. A good part of the public and many patriotic officials back then knew what was up and distrusted a federalized police force. Publicity, a.k.a propaganda, was used to allay their fears. Just like most of the public was against entering WW2 and was more anti-semitic than the average German Nazi. Propaganda was used change their minds or, more likely, convinced them that the rest the country had changed their mind and they were in a small minority of wrongthinkers.

I think it was actually the CIA that had a specific office/group that dealt only with consulting with directors regarding portrayal in Hollywood movies. Which actually would also explain the bad portrayal of FBI agents (Die Hard being the most obvious example)