The crisis years of the 1920s and 1930s offered the working class in several key countries the opportunity to make a socialist revolution. Misleadership and betrayal ensured that vital opportunities were lost. Fascism swept to power. Fascism was the price the working class paid for failing to take power itself. Fascism aims not just to repress workers or co-opt their leaders into running the system.
Fascists aim to smash to atoms the organised workers' movement.
For that you need masses of people. You need mass demonstrations of reactionary sections of the working class and middle class to surround the HQs of workers' parties and trade unions, as happened in Germany on the eve of fascist victory. You need police agents in every block of flats, every school or factory. You need these agents organised and rewarded by a mass party structure. To gain power you need tightly knit terror squads which can walk into meetings of hundreds of defenceless workers, beat up their leaders, kidnap and torture activists.