I strongly suspect the Russians had a hand in both the phony conspiracy theories and the actual acts themselves.
The Russians had the LEAST motive to kill Kennedy, they knew he was a lightweight and that’s why they put the missiles in Cuba and took Kennedy to the cleaners in the negotiations. The re-writing of Kennedy backing down the Russians was a joke, they ran circles around him and were happy to have such an inexperienced rube in the White House.
Oswald killed Kennedy, all the evidence points to him, modern forensics prove the shots could only come from Oswald.
The most investigated crime in the human history and STILL all the evidence points to Oswald.
2 people can’t keep a secret but somehow the “conspiracy” is still intact, never mind that all the conspiracy theories contradict each other.