Hitler and the weather defeat Germany in the east...not the Russians.
Last time I checked, General Winter and General Mud have yet to be defeated.
The weather is part of the war, the Germans were not well equipped to deal with it, the Russians were, so from that perspective the Russians did in fact defeat the Germans.
The Russians were able to move their factories well out of reach of the Germans and could have continued to produce tanks, airplanes, etc...
Eventually they would have worn down the German forces for two reasons, they had more to throw at the war and Germany was fighting on multiple fronts.