The basic template here is that the people (populism) become so discontented that they see no salvation in any of the existing elites or political movements, so they essentially appoint a dictator or an oligarchy to sweep it all aside in favor of <insert magical thing that will fix all their problems>. The level of naked authoritarianism and brutality varies between these movements -- some are more gloves-on and some more gloves-off -- but they all have an ultimately authoritarian character. The whole thing nearly always backfires into some form of "meet the new boss, worse than the old boss."
