I remember in 1968 a tabloid news paper (STAR? NATIONAL ENQUIRER?) had a front page story that Kennedy survived the shooting but was brain injured. According to it, Jackie married Onassis as he had a secret retreat on an island in the Mediterranean. It claimed he had died there and was buried at sea.
A fuzzy photo showed the island from a distance, and someone with a bandage on his head, sitting in a wheel chair.
This was quite a few years before the release of photos of a dead JFK on a hospital gurney.
My thoughts? If you want to kill a sitting President you don’t create a Byzantine Plot to kill him before tens of thousands as too many things can go wrong. You knock him in the head with a blackjack and push him down a flight of stairs. Only the lone crazed gunman does it in front of huge numbers of people. Andrew Jackson, Lincoln, Garfield, McKinley, Teddy Roosevelt, FDR, Ford, Reagan, are fine examples of the lone gunman trying to do it alone.
I would also add Bobby Kennedy to that list.
And Trump was almost assassinated twice by lone gunmen. The second was seen with a member of the Biden household staff a few days before he tried to kill Trump at his golf course.
I saw a (weird) documentary recently that said JFK didn’t die. But this theory was that he faked his own death, and Jackie was in on it. They retreated to Onasis’ Island. The reason was that he knew there was a target on his back by the Dulles Brothers and/or the mob, and his family was in danger.
The guy in the hospital photos was the cop, Tippit, who Oswald allegedly shot. Supposedly, he looked so much like Kennedy that his nickname admin police was “JFK”.
I notice you didn't include the Trump shooting to that list. An alleged lone gunman that wasn't a lone gunman.
I remember seeing that picture. My grandmother, not typically a reader of such things, bought this paper in the checkout aisle, because the article intrigued her.
My parents thought LBJ was behind the assassination.
My grandparents thought it was Cuba and the Mafia.
I have my own theory, which is much more sinister.