The thing about killing Lenin is that he was simply a member at the top of the pile for Russian Republicans. It is highly likely a USSR-like totalitarian Empire would have emerged no matter what given the Czarist history of Russia. However, if the leftists managed to win instead, it’s possibly that they could have avoided Totalitarian rulership. But that’s a lot of people to kill in order to allow a faction like the Trotskyiests or Black Army to win. And even if that did occur, given Russian culture, there’s no guarantee the state wouldn’t revert back to a Czarist-like totalitarian state.
Also, killing Lenin opens the door to Slavic fascist rule.
Well, not even the Germans could have predicted the large effect Lenin would have after being released. I don't think the Russian situation was particularly worse than what was happening in Turkey or China, or even parts of Mainland Europe (late in the war, that is). Getting rid of him might avert the black swan event entirely.