Do online lie-spreaders always believe themselves?

No, they don't. This is a good discussion. I personally believe, though, that in the bigger picture it's the true believers who are most effective.

There has been a lot of research on the types of people who believe conspiracy theories, and their reasons for doing so. But there’s a wrinkle: My colleagues and I have found that there are a number of people sharing conspiracies online who don’t believe their own content.

They are opportunists. These people share conspiracy theories to promote conflict, cause chaos, recruit and radicalize potential followers, make money, harass, or even just to get attention.

There are several types of this sort of conspiracy-spreader trying to influence you. - The Conversation