Epistemic status: very hand-wavy and vague, but confident there is a substantial and well-understood core. Hoping for an answer that elucidates that core more clearly.
It is something of a rationalist folk theorem that social movements face the risk of an "Eternal September", or of scaling into oblivion. (See e.g. this blog post by Leverage research, this paper by Owen Cotton-Barratt, David Chapman or Benjamin Hoffman on "Geeks, MOPs and sociopaths", and Scott Alexander on "the toxoplasma of rage").
I've had the sense that some cocktail of Hansonian/Dunbarian evolutionary psychology, basic game theory/microeconomics, memetic theory and Sturgeon's law, should predict this. That is, that some reasonably operationalised version of the claim "most social movements fail" is true.
Yet I am not able to point to >=5 historical examples of social movements that suffered this fate, along with some gears for what went wrong.
Hence I'm looking for links, historical examples, more fleshed-out gears, ... anything that might form a more rigorous reference point for an outside view on the fate of social movements.