It's not a question of total occupation, but to surrender, and that's achieved by reaching 0 NM. If the CPs don't accept the treaty after russian NM went to 0 with or without supporting Lenin, why do they get nothing at all, that's the question. What forces should be able to prevent the CPs from keeping what they already occupied in a broken down state?
Mostly the fact that it would be crippling for them to try and occupy an area that much (and yes, there should be more partisans forcing you to do this before surrender, even if there was no actual partisans in this war, occupation eats manpower. Also the fact, that it did not happened in this war. None of the losers get occupied, the Ottomans and the AH got dismantled, and Germany punished heavily, but not with total occupation and annexation, like what you want.
Also they get quite a lot (the entire Polish region goes to Germany) and Russia loses territory left and right (Finland and others), if you help the Fins, they even send trade convoy with quite a nice booty.