JFK also shared a girlfriend with Giancana (Judith Campbell), and she ran Anti-Castro money and marching orders from JFK to Giancana.
Frankly, all that proves is that they had connections. I'm all in on the Mafia did it, if there was a conspiracy (which I'm much less sure than I used to be), but I'm not totally convinced that Giancana would be at the center of the mafia side of the plot.
In any event, the concurrent ties between the Kennedys and the mob, and RFK's anti-Mafia assault as AG, is one of the strangest and most baffling phenomenons in recent American political history. The mob ties were both personal and functional, with the Kennedy's using the mob in anti-Castro activities, while at the same time RFK is snatching up Carlos Marcello and dropping him off in a jungle in Guatamala (the birth country in Marcello's obviously fraudulent immigration docs). An extreme and foolhardy move that the courts even overturned.
I've read more about the Kennedys and the assassination than most, and more about the mafia than almost all. And both of those phenomenon existed at the same time, its almost universally accepted. And yet, I've heard almost no explanation, credible or not, for WHY those two obviously diametrically opposed initiatives were happening at the same time. How did JFK and RFK even sort out the contradiction among themselves?
If RFK's actions were purely symbolic lip service, that would be typical politician sleight of hand, but it's clearly obvious they were not, so how did the brother team even begin to reconcile that? I've seen precious little attempt to make sense of it, in an area of "study" that invites even the wildest claims and explanations.