The stated reason was to plug the leaks (plumbers) coming out of the White House resulting in things like the Pentagon Papers. This was not a political act by Nixon. Nixon had zip involvement in it.
Nixon wanted the ILLEGAL leaking to stop. The Pentagon Papers had nothing to do with Nixon and his administration, but it was still a treasonous National Security threat. But then came another leak, this time involving secret negotioations with the Soviets about nuclear weapons reductions. It actually stated actual US missle strength and even some secret locations. Thats when he really got pissed and the “plumbers” were formed, a totally legal effort to stop the leaking. Now, the idiots that were hired did some stupid, illegal stuff but Nixon never ordered or was there any proof he knew anything before hand. The only one that was really directing anything from the start was JOHN DEAN...he was the one running this thing from the start. Very suspicious. Then the so called “deep throat”, Mark Felt, committed felony after felony by leaking to the press. Theres so much more to this...