It’s hardly controversial. Marx envisioned that a revolution would happen when the working class (the majority of any society) becomes class conscious and usher in socialism. That in essence would be a vigilant population.

The issue with popular presentation of Marxism is that what is presented is actually Leninism. Lenin is the one who thought proletariats can’t become class conscious (or vigilant) on their own and instead require a vanguard party of revolutionaries to lead the proletariat into communism. How that worked out is evident from the USSR.