The movie JFK is basically a documentary (with many wrong details) and is the reason for the law that lead to these files being released.
You know how people say it would be impossible to cover up something so big? It would have to leak?
Well, it did. The CIA/Mafia/Cuban assassination connection is firmly established fact now. Among many other important facts use to be "conspiracy theories."
Motivations tl;dr https://i.imgur.com/WEjm2ig.jpg