Most of what QAnon believes is what the American right wing and many Conservative/Evangelical Christians already believed - particularly in linking secular society/leftism/"globalist elites" with pedophilia and conspiracies of satanism. None of that is new, some of it is very old indeed. In my day we just referred to it as the "New World Order."
What's new is how QAnon packaged and rebranded these disparate bigotries into a single narrative with Donald Trump as the messiah and made it viral, likely on the back of the general alt-right and neo-reactionary surge of support within Trump's base. But it wouldn't have taken off at all if that wellspring of hate in America's core hadn't been there to tap, and there weren't already plenty of people who would have found the general premise of, say, Hillary Clinton drinking the blood of child sex slaves, to be reasonable to begin with. You don't convince people to believe that sort of thing who aren't already halfway there.
I would strongly dispute that "many" Evangelical Christians believe that secular society, leftism, and global elites are linked to either pedophilia or satanism.
Nor was that the idea of the "New World Order". Globalist elites? Sure. Secularism and leftism? Yes. Conspiracy? Absolutely. Pedophilia and satanism? No.
Rumors about satanic rituals came up everywhere from Denver International Airport to Skull and Bones and Bohemian Grove to the Bilderberg Group... at least wherever NWO conspiracies overlapped with the Evangelical demographic that took things like Left Behind and John Hagee seriously. The satanic panic happened in the 1980s.
Maybe "many" is an overreach, but those beliefs were definitely present well before Pizzagate and Qanon.
I would bet that an event like Jeffrey Epstein being suicided in federal prison under impossibly suspicious circumstances -- after it came out that he had been running a child sex trafficking ring of immense scope, been granted a sweetheart deal during his first legal run-in in 2007, and had close ties to the uppermost echelons of wealth & power including Bill Clinton, Donald Trump, and Bill Gates -- has probably also greatly expanded the number of people willing to take the theory seriously. Alan Dershowitz even says he was introduced to Ghislaine Maxwell by Lynne de Rothschild herself!
What's new is how QAnon packaged and rebranded these disparate bigotries into a single narrative with Donald Trump as the messiah and made it viral, likely on the back of the general alt-right and neo-reactionary surge of support within Trump's base. But it wouldn't have taken off at all if that wellspring of hate in America's core hadn't been there to tap, and there weren't already plenty of people who would have found the general premise of, say, Hillary Clinton drinking the blood of child sex slaves, to be reasonable to begin with. You don't convince people to believe that sort of thing who aren't already halfway there.