A few years ago it came out that Deep Throat was Mark Felt -- he had been #3 at the FBI. Felt was disgruntled that Nixon had passed him over for promotion after JE Hoover died, and so carried out a leak campaign through the Washington Post that ultimately brought Nixon down.
The Post editors and Woodward & Berstein knew who Felt was. They chose to keep quiet and accept decades of hero-worship. The truth was that they were willing participants in a rather slimy and petty act of political revenge.