I think you may be overstating the rise of conspiracy theories throughout the '00s, or rather, understating their weight in previous periods.

If you want to point to the marked rise of conspiracy theorists then you have to at least stretch back to the Kennedy assassination. This is easily the most widespread, actually believed theory, and its impact on people at the time was monumental.

The moon landing theories are obviously prevalent, though likely with fewer true believers and less implications on them.

Even in the 90s this was a rampant thing. Columbine shootings. Cobain's suicide. AIDS.

I would posit that conspiracy theories are a byproduct of mass media. However, you could easily stretch it back further and draw parallels to witch hunts as being attributable to earlier conspiracy theories on a smaller scale.