What's really tricky is that Lenin is changing both the future and the past here. Why is that tricky? Lenin is both responsible for learning the science of communism from the future (assuming Stalin remains in the future of Lenin's timeline here, by no means a safe assumption) and then transmitting that science back to its inception (making another not particularly stable assumption that Marx is in the past).

Taken at face value it's just a grandfather paradox with ideology instead of biological reproduction and Lenin as the fulcrum.