i think the mafia had good motivations to kill him and his brother, the mafia was at its peak at that time
the fact kennedy was tough on the mafia meand nothing, maybe he took the votes and they betray them
of course the mafia if involved was not alone, but it planned the murder togheter with politicians, member of cia or some oil boss
according to an informant in the sicilian mafia, enrico mattei was murdered coz some american oil bosses wanted him dead and he said the murder of mattei is linked in a way or another to kennedy murder
but who's knows