Most of the people I've talked to aren't crazy alien conspiracy theorists so I can't really comment on that brand of conspiracy theorist. Honestly my main experience is the standard 9/11, global warming, and Obama conspiracy theories (which were incredibly racist) from the early to mid 2000s and those were all pretty similar to modern theories and at least for my father in law and his friends were definitely from Fox News and talk radio.

Edit: a good example to me was the start of the birther movement, which is a quinessential modern conspiracy theory to me, and I remember that as talk radio and Fox News.

Global warming and birtherism were a turning point. It was then than condpiracy theories were directly applicable to politics. Managing them then became a practical political weapon.

The John Birch Society predates both, and was a similar movement by similar people towards similar ends.