The New York Times has a good look at how one particular conspiracy theory, a completely false notion that ex-FBI director James Comey said Trump did not ask he halt the Flynn investigation in his mid-May Senate testimony despite Comey in fact asserting no such thing, ricocheted around the usual conservative sites in a transparent hoax. It started with troll Jack Posobiec, who simply made it up. Breitbart and Alex Jones jumped on it and soon it made it to Rush Limbaugh and, of course, Fox News' Sean Hannity.
It was an absolute fraud, and one that could easily have been proven a fraud by anyone who bothered to check—and it's difficult to believe that the entire staff of Breitbart and Sean Hannity's show were so uninformed as to the explosive nature of Comey's testimony that they could have plausibly believed it in the first place. Comey's testimony about Trump pressuring him to drop the investigation was the top news story of the day; peddling a tweet from a known hoaxer that claims the exact opposite can't be described as "falling for" a hoax. It counts as being an accessory to it. Sean Hannity and his ilk were spreading the false version on purpose.
In an email, Mr. Posobiec described his work as “reality journalism — part investigative, part activist, part commentary.” A day before his tweet, the White House had allowed him into an Oval Office photo op with the president, and he tried to ask a question about Seth Rich, the murdered Democratic National Committee staff member.
The reason for peddling the hoaxes is simple: Many or most of their followers will believe them. They won't check. So it doesn't matter whether the news they present is entirely fabricated. They will get the desired effect—angry conservatives obligingly believing the conservative president has been vindicated—and suffer no consequences no matter how quickly their claims are proven false in other venues. It helps when you have an administration eager to help the effort. It helps more to have already pre-segregated news markets such that conservative fans aren’t likely to ever find out you’ve lied to them.
“The ability to mitigate such disinformation campaigns was far easier in the 1990s,” said Chris Lehane, who worked as an aide in the Clinton White House. Back then, he added, “for the most part the existing distribution channels were not as segmented across ideological lines that, in effect, create parallel realities that run along ideological grounds.”
It's a conservative propaganda effort. It's the dissemination of provably false information up and down the conservative "news" chain, from the lowest dregs to the Fox News cameras, facilitated by a conservative movement so contemptuous of mere objective reality that they don’t just tolerate, but demand they be given more pleasing versions.
The Times doesn't touch on just how frighteningly dangerous the embrace of such tactics is. It is the cornerstone of authoritarian, fundamentalist, and fascist governments. When the government and their compliant media figures simply alter the news to best benefit the party, that's the end of things. Democracy cannot exist in such places, and there is no informed consent of the governed if the governed are simply given whatever false information will render them most compliant.