Who stood to gain the most by the demise and/or removal of JFK?
Fortune smiles upon those who actively seek greater gain. Denied the nomination in 1960 by some backroom shenanigans at the Democrat National Convention, with only a small bone tossed his way from the Kennedy Mafia, Uncle Elbie Jay was no stranger to using extralegal ways to either assure personal advantage to himself, or to cover up his earlier extralegal activities.
Elbie Jay did not pull the trigger himself, but he almost certainly knew who to call in order to set the series of events into motion.
And it wasn’t Bobby Kennedy.