Why else have we isolated Cuba so completely, for so long? We held summits with the Soviets and Chicoms, but not Castro. Cuba is probably the only country on earth where Americans need to get government permission to travel to.
It's an established fact that the Kennedy's, John and Robert, were trying to kill Castro. That he might have known about it, and decided to return the favor, is only logical.
JFK did JFK a huge favor by withdrawing support for the Bay of Pigs. Hell, the Soviets didn't even know who Castro was at the time.