Marcello allegedly told Frank Ragano, his lawyer of many years, that he had JFK killed to get back at Bobby Kennedy for deporting him to Guatamala but he also lamented that he should have gone after Bobby, not Jack.
Correction. Ragano said that Santo Trafficante said this about Marcello. It should also be noted that the FBI had notice of an assassination plot on Kennedy a few days earlier in Miami.
I will say this about Oswald - he was involved and the proof is that he left his wedding ring and almost all his money on the dresser for his wife Marina before going off to the Book Depository building. An innocent man would not have done that.
Beyond this, it’s all speculation.