Why does communism require a dictatorship of the proletariat instead of democracy?

According to Osho, communism calls for a 'dictatorship of the proletariat' because democracy, dominated by money, preserves the status quo: the rich finance elections, buy politicians and even votes, keeping the poor powerless. Only when the have-nots hold decisive power can exploitation be stopped and a class-divided society be transformed toward classlessness; hence Marx’s proposal—distinct from fascist dictatorships—as a strategic seizure of power by the poor.