Social movements come in all sizes. Its a bunch of people who all agree on something. That is a social movement.

You can call it a subculture or philosophy or movement, but social movement to me implies something with broad appeal.

Agreed. If society is unmoved, it wasn't a social movement.

It sounds like you're saying social movements by definition can't fail, which doesn't seem like the most sensible definition to me

Man who refers to Heaven's Gate as a social movement