No question. Shots happened, <snipped irrelevant assumption>
… why?
Because he had a gun.
What was his motive? We cannot know, but there are lots of non-conspiracy possibilities that are more than sufficient as to render any conspiracy theory unnecessary.
What does any lonely loser want? Respect, fame, notoriety, to stand out from the crowd, to differentiate himself from all the other sad losers.
What motives do assassins through history have? We don't often find out, but we have some data. Political effects are a common, but far from an exclusive, motivation. Perhaps his motivation was religion, or insanity (but I repeat myself).
A grand conspiracy is simply unneeded to explain the event; Maybe the shooter was trying to make Jodie Foster fall in love with him. If John Hinckley had died at the scene of his attempt to kill Reagan, would we ever have guessed his motive?
Nutters do nutty things for nutty reasons. Speculation is all well and good, but the only path to the truth is evidence, and in the absence of evidence, no amount of navel gazing or hypothesizing will ever get us there.
Before we allege conspiracy, we need evidence of a conspiracy. The mere fact of a shooting isn't even close to being enough evidence to make that allegation.
Sometimes the very best answer to a question is "nobody knows". Humans are remarkably adamant in their dislike of that answer, even when it is the only reasonable position to take.