Where would the Kennedy conspiracies be without the internet? Oops, that's right there was no internet back then.
Was Kennedy's assassination any more earth-shattering than 9/11? About the same on the WTF scale, if you ask me.
Back then we didn't even have cable. There were a couple of large chains of independent TV stations, i.e. not affiliated with the networks, but even those would be considered MSM today. Yet the voices on the conspiracy side about Kennedy found an audience. There were mock trials on TV, pamphlets, magazines, books.....
All of those would be what the truth movement would be up to, today. It might have taken a little longer to spread the word, but like the Kennedy conspiracies, only a couple of years, and by now, five and a half years later, they could conceivably have the same following. Actually, with cable and all the various requirements to allow community access to public broadcasting (which didn't exist in the mid-60's), it would've probably spread faster than the Kennedy stuff, which was well into the popular media by late '66, IIRC.