Marx was not a future teller. The revolutions are, indeed, caused by class struggle, but we learned trough time that to occur, a revolution need some objective and subjective conditions. (Lenin) The revolutions we experienced happened mostly on underdeveloped countries, contradicting Marx’s previsions.

The most developed economies tried to minimize it’s contradictions home, while exporting them to other countries, (also Lenin, Imperialism) avoiding the development of subjective conditions to revolution. (Henry Ford and Keynes play a crucial role here)

After the colapse of USSR neoliberalism put a end on this policy, and now we see a surge of revolt on developed countries because of the increasing contradictions under neoliberalism.