This explanation falls apart when you look at the crazy conspiracy theories about chemtrails, fluoridated water, population control, etc, etc. There's no optimism to be found there, just distrust of authority and/or fear of things (science, usually) they don't personally understand.

I believe fear drives conspiracy theorists, not optimism. Concerning school shootings, it is absolutely terrifying to know that your children's school or your spouse's workplace could be the next target of a school shooting, and there's nothing you can do about it. Believing that these incidents are staged allows you to believe that they can't happen to you or your loved ones.