The CIA and FBI knew this and were monitoring Oswald. So, yes, both agencies had a role to play but it isn't what Tucker and the Left assert.
The JFK assassination wasn't that long ago. People Oswald's age at the time are still alive.
Communists are a savage lot who never forget and never forgive.
You can't just go releasing information that would reveal the identities of people involved, their families and friends.
You obviously can't go releasing details of how human intelligence was gathered domestically and abroad either.