“Why could there not have been two assassins, independent of each other from two separate orgs that wanted to kill JFK?”
Well, you’re not just adding improbabilities there, you are multiplying them.
Say, disregarding all other variables to keep it simple, there were 10 days that anyone could have chosen to try to assassinate JFK. The basic chance that some conspiracy chooses any day out of those ten is .10 or 10%. The basic chance that two conspiracies both pick the SAME day out of the ten is .10 * .10 = .01 or 1%.
That’s just to show how a single coincidence multiplies the improbability. There would be other variables, like choosing to try to assassinate him in the first place, and the time of day or particular spot and method to use. Pretty soon you’d be dealing with infintessimals.
But, it could happen..................