Ol’ Fidel is toward the bottom of my usual suspects list. Lotta people/institutions had motivation, so it’s hard to choose from the rogue’s gallery.
An article I read a few months after the assassination claimed that JFK was shot by mistake. Oswald was after John Connally, then Gov. of Texas. WTF??
The author then proceeded to lay out that Oswald petitioned Connally multiple times to get his discharge reinstated as Honorable (went to "Dishonorable" when he tried to defect to Russia). He couldn't get anything under the GI Bill, loans, mortgages, etc. There was also a problem with immigration and his wife. Connally wouldn't do anything and passed the buck on both.
I always thought it would be ironic if that was true, the real coverup being that JFK was killed by mistake, and wasn't the martyr the Media and Powers That Be claimed he was.
[Sidebar] The FBI took Oswald's Carcano carbine and did rapid fire tests with it, concluding that he could fire rapidly with it, which was one of the sticking points. Some months before, I had bought one and after shooting it, felt that it was a piece of crap. I read later on that because the bolt handle closed 2" forward of the trigger, people in the gun community declared it was a lousy weapon for rapid fire.