For the purposes of the AHC, the answer to any questions of the how is "Handwavium" as I'm not sure what precisely in Soviet internal politics has to change and I'd yield to more knowledgeable people on that regard. The challenge is that in this case the Soviets smash the entirety of Army Group Center in a local assault aimed at that Army Group in the wake of their counteroffensive in front of Moscow. What, realistically, happens after that? Germany obviously has taken a huge, immense loss, but so has the USSR in terms of both manpower and materiel. This is months before the USSR gets the trucks and the like it needs for logistical power-projection at a great scale across its borders, and the Germans as 1943 IOTL showed have at least the capability to produce a huge *quantity* of soldiers if dire necessity mandates it.
So if the USSR manages to wipe out Army Group Center, what would be the realistic overall impacts of this for WWII as a whole? Rommel and his war won't change one way or the other at a tactical level at this point, but how big a disaster would the full Soviet success at Moscow have been for Germany? How much would the USSR in the wake of its 1941 losses have actually been able to do against the Nazis?