Most of it seems to be wild speculation. Much of it seems to be an Argument from Ignorance fallacy. As in "I cant see how a single gunman could have possibly got off three shots and a head shot. There must have been another gunman". Most people cant understand, or worse wont try to understand, the complex dynamics of the workings of this world, and that drives them towards these simpler solutions. Then, once they latch onto one of these conspiracy theories, they will cherry pick, anomaly hunt, and make every tendentious argument that they can. At least that's
been my experience.