And then he was shot by a leftist Commie. Oh the irony.
Even more ironic, Oswald put into power a president who was one of if not the most liberal president in US history. The first thing LBJ did as president - the first - was push for passage of the civil rights bill, something the far right in Dallas hated JFK for pushing.
Then he passed the "Great Society" legislation - civil rights, housing rights, voting rights, poverty programs - all of this vehemently opposed by the Bircher right. Even more, LBJ essentially ended the covert war on Cuba - Operation Mongoose. All of that nonsense was pushed by the Kennedys and RFK stopped advocating for it.
So these far right wingers killed JFK because he was too liberal on civil rights and too soft on Castro. Then they put into power a president who was even more liberal on civil rights and softer on Castro. Irony of ironies.
The conspiracy believers - the Oliver Stones and others - never mention all of this. For them it's all about Vietnam. Well, LBJ didn't send in troops there until late 1965 after the South Vietnamese government essentially fell apart and Hanoi and Moscow stepped up its aggression.
Part of the problem reasoning with these conspiracists is trying to straighten out their bizarre conspiracy history. They believe things that are simply not true.