Somebody did talk.
His name was John Martino. In 1963 he was an anti-Castro militant who mixed with organized crime figures and CIA officers. His story is one of the clearest indicators that opponents of JFK’s Cuba policy had foreknowledge that President Kennedy might be assassinated in Dallas.
To put it another way, those who doubt there was a conspiracy need to address John Martino’s story. It is corroborated in multiple ways.
Martino, a native of New Jersey, was a petty racketeer as a young man with arrests for gambling and loan sharking.