The most reasonable idea about a conspiracy is that the CIA/FBI knew Oswald had contact with the KGB, were embarrassed they didn't stop Oswald before he acted, and the CIA covered up what they knew about Oswald's Russia/Cuba ties.

This is much better than the least likely consipiracy: Kennedy's head just inexplicably exploded on its own.

Wow, can't believe this is the first time I've heard of this. It actually makes a ton of sense and explains away alot of issues.