1) Literate people who care about history and know that industry does what's best for profit at all costs.
2) People who don't read much looking for a hobby.
3) Liberals hoping to pass off their empty skepticism as allegiance to the mainstream.
For instance, all theories about 9/11 are conspiracy theories in the literal sense. Even in the official 9/11 Commission Report theory, a bunch of men conspired to hijack airplanes on the same day and crash them into buildings. That's literally a theory about a conspiracy. But in the new meaning, this is not a conspiracy theory because it's the government's officially endorsed theory.
Whether the CIA induced this verbal judo deliberately is another question. I'm inclined to think they didn't. I think it was a natural language shift, albeit one that has been harmful to society.
This part got an audible "Heh" out of me though: "Note that Robert Kennedy, Attorney General at the time and John F. Kennedy's brother, would be the last man to overlook or conceal any conspiracy." Robert Kennedy was murdered one year after this document was written, while running for president. Suppose he secretly doubted the Warren Commission's report (as has been claimed by some of the people close to him, but disputed by others), becoming president would have given him a uniquely privileged position from which to assail it.
No one (the public) had heard that term before the CIA got US media writing propaganda pieces to disparage inquiry into the assassination. It wasn't about the theories. It was about defining a group of theorists and creating ways to dismiss them. That continues to this day in yearly exercises of establishing mainstream credibility where young "journalists" help us all understand the broken psychology of people who want the world to be scary.
Honestly, if you have ever tried hard to advance a line of thought that's dangerious to the establishment you'd maybe be personally familiar, as I am, with the smell of counter-intelligence. But I can't cite a web link that would make that credible. And you've already learned to discredit anyone calling themselve a truther.
It worked. I'm saying it worked because it works on me. No amount of facts or scope or wisdom makes mainstream friends of mine more open to reality. Reality is scary. Disagreeing with the 'news' is scary. But US industry gatekeeps history and I refuse to be naive.
The ol' "conspiracy theory conspiracy": https://apnews.com/article/fact-check-conspiracy-theory-jfk-...
It doesn't matter if the phrase existed before hand, it very obviously blew-up during the JFK event.[0]
It could entirely well be that the DoD didn't invent the phrase, but it's pretty obvious that it very quickly became a part of the public verbage during heavy interest in the JFK event -- that trend could have easily been the indicator of work towards the discrediting of both the term and those that had too much curiosity towards things they shouldn't question.
[0]: https://books.google.com/ngrams/graph?content=conspiracy+the...
https://books.google.com/ngrams/graph?content=conspiracy+the...