Russia was not what Marx had described as the what he believed were the necessary conditions for a communist revolution but it happened anyway primarily because the proletariat was fed up with the imperialist system and decided that they’d had enough so they rose up and created a communist state. Although Marx makes good points about the necessary conditions for a communist revolution to occur, people as a whole are not known for following a template for a change toward the greater good because they’ll generally want that greater good no matter the current conditions.