The military had spies in the White House during the Nixon administration.
Alexander Haig, a general, ran the country for all practical purposes while Nixon melted down.
Other little known facts:
1. Haig controlled the White House safe that held the notorious Watergate tapes which brought Nixon down
2. Bob Woodward, the famous Washington Post journalist who broke the Watergate story, was a Yale grad, a Navy officer, a likely NSA officer, and a briefer to Alexander Haig when he was in the military.
Small world isn't it.
For more info on this see the book "Silent Coup" by Gerald and Deborah Strober.
It's a distinct possibility that the US military wanted to get rid of Nixon and went ahead and did it.