I would suspect the failure of most social movements is overdetermined. Social movements by default are designed to change the status quo, and the status quo tends to be stable and intrinsically resistant to change. Social movements are often ideologically originated and may be aimed at achieving something practically impossible.
Another phrasing might be that most social movements fail because a sober analysis would have shown that there was never any realistic possibility for most social movements to succeed, even if they had more resources, smarter people and better planning.
I would suspect the failure of most social movements is overdetermined. Social movements by default are designed to change the status quo, and the status quo tends to be stable and intrinsically resistant to change. Social movements are often ideologically originated and may be aimed at achieving something practically impossible.
Another phrasing might be that most social movements fail because a sober analysis would have shown that there was never any realistic possibility for most social movements to succeed, even if they had more resources, smarter people and better planning.