Well, not exactly Qanon in itself, but the idea of a deepstate and other beliefs that 1/3 of the population holds variably stem from Qanon or hold similar belief structures. Here's the article:
https://www.ipsos.com/en-us/news-polls/npr-misinformation-123020
Now, that's not me saying 100% that 1/3 of Americans believe or believed in Qanon, but I wouldn't be at all surprised if it was within 10% of that range. Hell, you watched the documentary, you can't be all that surprised that at the very least, several million americans believe it. Fuck, Billions believe that a magic sky daddy shoots prophets onto earth, and that donkeys talked and stupid religious bullshit like that. Would it honesty surprise you if people started turning their religious beliefs into political ones? That's exactly where you're headed btw.