The most basic aspect of the conspiracy theory is that it bypasses the obvious reasonable explanation and vanishes down a rabbit hole of complicated alternative explanations that make no real sense but allow the conspiracists to avoid dealing with the implications of the actual event that took place.

Leftists did not want to deal with the fact that JFK had been murdered by one of their own. So they invented a bunch of alternative conspiracies involving the CIA, Cubans and other "right-wing" villains. These conspiracies allowed them to avoid dealing with the violence at the heart of the left. But that violence continued to spill over anyway leading to riots and terror plots.