"'It simply doesn't make sense that we all got played,' said another user on one of the biggest QAnon channels on Telegram."
Well, actually, it makes perfect sense!
On a slightly more serious note, the key lesson here is that if you want to run a successful millenarian cult/conspiracy theory, you don't want to tie yourself too closely to a highly specific prediction that can be readily falsified. What's happening to QAnon is similar to what happens to movements claiming, e.g., that the apocalypse or the Second Coming are going to happen on a specific date in the near future, or those who claim that a specific individual is the Messiah and the like. When the big day rolls around and not much happens, disillusionment quickly sets in. Ditto if your messiah dies or falters.
I'm not aware of even one movement that made clearly falsifiable predictions tied to specific dates and/or currently living people, that then evolved and survived. By contrast, movements that avoided such highly specific predictions (communism, fascism, various charismatic religious movements, etc.) have thrived far more often. It is true that some people initially attracted to the former often end up switching to the latter.
But it's too early to celebrate. QAnon may fade. But the kinds of people attracted to it may well instead just gravitate to other similar movements, including ones that don't make the mistake described above. There are plenty of options on both left and right. Nancy MacLean's left-wing conspiracy theory about how the Koch Brothers and a small cabal of other libertarians secretly dominate American politics has a lot more respectability than QAnon ever did, and is believed by considerably more influential people. Ditto for right-wing conspiracy theories about Big Tech, Soros, and the like.