Why did Vladimir Lenin want to end Russias participation in WWI?
Lenin was in exile when the war started (due to his revolutionary writings). It was the Germans who helped to smuggle him back into Russia. Once there he was able to use the sentiment of unrest caused by the war to lead the people toward revolution. Once he had gained control of Russia he wasted no time in declaring peace with Germany. His reasons were first, as payback for their assistance. Second, because the war was seen as a fight between the imperial families of Europe, he (and others) felt that the war had nothing to do with the ordinary people, and so expecting them to go off and die in such a war was wrong.
Two reasons. One, the ideology of communism refutes nationalism, which is the basis of warfare between states, and instead says that the world is driven by class relations. To communists, it didn’t make sense for the Russian lower class to be fighting the German lower class in trenches, because they are actually natural allies against the aristocracy of their respective states. Also, the Russian people wanted to get out of the war, and they were ready to overthrow old governments and support new governments on the promise of ending Russian participation in WW1. So Lenin promised to get Russia out of the war, and the people supported him when he staged a coup.