I think there is a whole class of conspiracy theories being left out, and I classify them as anthropomorphizing social phenomenon. This is the "They" that we hear so much of. To me, when a person subscribes to one of these theories, I don't think it necessarily makes them particularly gullible or crazy. It's just very difficult for human beings to understand complex, emergent phenomena without ascribing some kind of teleology to it—a single mind (or small group) behind it all.

Even language makes this difficult. Ask someone to explain natural selection to you, sometime.

So, what we have in many cases are various changes in our society, some of which are truly unintended consequences of some government policy or invention; then, throw in some group that benefits from this change, either unintentionally or because they were able to recognize and seize an opportunity, and that's all you really need for some people to think that "They" were behind the thing, all along.