Indeed.
The major problem with a conspiracy is the difficulty of keeping it a secret. Especially now, when the man who discloses the facts will become rich and famous.
I am not one to believe the CIA men of 1961-63 (CIA being shorthand for all the shadow warriors from agencies known and unknown) were Nazis, or traitors. Most of them were patriots, and courageous ones at that.
What if someone made up a story (or what if it was really true) that JFK was compromised by his sex life, or his drug taking, or who knows what, and that the failures in Cuba, and SVN, and Laos, and Tibet were the result.
What if that someone were DCI, or the FBI Director?
Do you think there would have been an impeachment, and a Senate trial? I don't.
Do you think, given the choice between a live traitor and a dead hero, that his brother would have aggresively pursued the truth? I don't.
This crime will never be solved.