Great question.
The answer is that JFK was about to dump LBJ from the ticket and was investigating him for a bunch of felonies involving Bobby Baker.
https://en.wikipedia.org/wiki/Bobby_Baker
If you notice all of the key players did not just have something to gain by the assassination of JFK.
They all had a lot to lose if JFK was around for much longer.
"Baker, however, was convicted of tax evasion and spent 18 months in prison." - Wiki
So Baker was involved with the assassination to hid his 'criminal wrong doings' and he still went to jail?
"They all had a lot to lose"
Involving yourself in assassinating the President seems like a lot more to lose than just getting caught in shady business deals.
18 months in prison for business fraud vs. execution for treason.
Johnson was up to his neck in so much criminality. He’s lucky he didn’t go to prison. I guess Nixon wanted the whole thing out of the way.
Going all the way back to 1947, if not before.
I seem to remember some kind of sleaziness that Nixon was involved in, when he was in the Navy. Pretty tame compared to the things Johnson was doing out in the middle of nowhere, in Texas.