I still think the mafia was behind it all.
Kennedy's old man was a bootlegger with ties to the mob. There were a number of reports that Kennedy was only elected because of "ballot box" stuffing in Illonois by the mafia.
The mob lost billions when Castro took over Cuba and kicked them out. I feel that there was an agreement between Joe and the mob that his son would get them back into Cuba. The Bay of Pigs was the answer as botched up as that was.
After that, the mob got tired of waiting....that is my view anyway.