[Smokin' Joe]

Even Watergate`s “Deep Throat” came out before he passed on.

No one was killed in Watergate.

Higher stakes make for tighter lips.

Recall, Mob interests in Cuba were lost when someone called off air support for the Bay of Pigs invasion. Millions in nightclub action were lost to the Communists' regime as well as smuggling opportunities.

There were plenty of reasons for people to keep their mouths shut, and an accident here, a suicide there, an unfortunate plane crash, all add up over time. People 'in the know' might even have died of old age.

[ARepublicanForAllReasons]

Lots of groups had reason to be PO'd at JFK: Dixiecrats, CIA insiders, but especially the mob families, who were double crossed as well by little brother Bobby as AG.
I don't know if LBJ was in on the planning, but the fact that the assassin was himself assassinated within the day (clearly to shut his mouth for good) indicates a conspiracy.
Sure, there are lots of lone assassins with Marine Corps shooting skills lurking out there, but how many have access to the Presidential parade route and access to key buildings, as well as travel money to follow the Prez around? Lone assassin is almost an oxymoron in the JFK assassination case.