I'm not so sure about this explanation; people believed in conspiracy theories in the past. Witch-hunts for example are fundamentally not that different from Q-Anon and all of that bollocks: "mysterious dark forces do evil stuff when we're not looking".
The whole "they're abusing our children" is also a trope that goes back a long time, most recently during the 80s with the whole "Satanic Ritual Abuse" stuff. That was much worse, because innocent people's lives were complete wrecked over what was complete bollocks. Pizzagate is near-identical, with s/daycare/pizzahut/.
More examples can be found throughout history – they're typically not called "conspiracy theories", but often they're not that different at its core.
I think what social media has done is allowing people to reach a wider audience. That person outside the grocery store reaches what, maybe a few hundred people with several hours of work? On the internet you can reach about 1.5 billion English speaking people with a minute of work. And that person outside the grocery store has no real way to organise a meaningful community, even if they do manage to gain 2 or 3 acolytes. On the internet you just create a Facebook group, or reddit sub, or whatever.
And all of that is including only the "crazy people". Add bad faith actors to the mix spreading misinformation simply to cause chaos and things quickly become well fucked.