[simias]

I think your analysis is accurate. These past years reddit's "The Donald" community is a prime example of that, except it went through all phases in about a year, maybe even less.

But I also think you need to take into account that many of the original users who genuinely did not seriously believe the "Hitler did nothing wrong"/"Hearth is flat"/"Donald Trump would make a great president"/... meta-joke end up leaving when things get serious. It's actually a feature for the extremists who push these ideas, if you're not with them you're against them, it's all about creating an echo chamber at this point. Reddit is terrible for that because of the moderation and voting system but even on 4chan good luck trying to argue against the hivemind, you'll just get insulted over and over until the thread 404's. Eventually you give up and stop bothering.