We had this massive authoritarian populist right wing movement a few years ago that really exploited the fact that a huge number of Internet-naive people had just been brought online via the mobile/tablet revolution. These people had never been exposed to memes (in the Internet parlance), troll culture, conspiracy theories, propaganda bots, click bait, and all the other tools of the Internet influence trade and were easy pickings for a loosely organized confederation of "alt-right" propagandists.
As this happened I watched a surge in analytical takes on this from both the left and from anti-authoritarian libertarian (a.k.a. actual libertarian) circles. I saw podcasts that had formerly discussed conspiracy and fringe ideas in a detached "Art Bell" style pivot and go "meta" on these theories and start digging into their intellectual and cultural origins. I saw books like "It Came From Something Awful" that analyzed these phenomena become bestsellers in more mainstream circles.
All that analysis was the immune system working.
The Pepe the frog movement was a one off thing. It won't be repeated. I doubt we will see anything as explosively successful as Qanon again either. Sure there will be things like that on the fringes but something that vaults from a dumb 4chan LARP into a nationwide movement within a month or two is not likely to happen a second time. The population has already been exposed.
China on the other hand... if this is what they are doing and if they are actually successful at it, they will remain deeply vulnerable to an outbreak of this type of propaganda whether it originates from foreign or domestic sources (or most likely a mix thereof).
P.S. I think the strongest argument against deplatforming is that this is interfering with the process of memetic immunity. Given that we have no vaccines against toxic memes (or even a theory of how that would work), letting the population get exposed and achieving herd immunity is probably the best strategy. So go ahead, let tons of naive "conspiracy virgins" get sucked into Qanon or whatever. They need to build up their immune systems.
I rolled my eyes instantly at Q because I knew chan culture and I also recognized a grab bag of worn old conspiracy tropes from Usenet in the 1990s. I saw all that stuff when I was fifteen.
I've changed my mind on deplatforming multiple times, but I think this is where I've settled as I've watched everything play out. Democracy, if we let it function, is antifragile.