LBJ left because he actually thought he was in charge.
Bush41 convinced him otherwise.
Nixon was a placeholder
What? Bush 41 was a bundler for Nixon, cost him his senate run and would have prevented him from becoming president but he managed to put it deep in the closet. Because the money he bundled went into that famous so-called slush fund, and a good deal of it (couple hundred thou) came back to his campaign.
(Roger Stone’s book has a lot of great info on this kind of stuff.)