I believe this is similar to working with the Russians in WWII. They are allies, but each ally is in it for the reasons of self preservation. Make no mistake, the DS is as big a threat to Putin as it is to the rest of the free world. If it benefits Russia to work with the DS for a time, Putin will do so. If the DS gains too much power and becomes a threat, Putin will reassess his position. He has done so. This is geo-politics. It is chess on a global scale. Alliances are made and broken depending on circumstance and risk. Putin is not a fool, nor is he a benevolent missionary doing things to benefit all human kind for the sake of warm fuzzy feelings. He is always doing what is best for himself and his people.