Everyone has an interesting point of view and comments here.
Moscow as a lynchpin, is given too much emphasis by its enemies, and by commentators before and since. Yes, the loss of Moscow would have been a major blow to the USSR, but as the Ural-Plan and Barbarossa show, no one angle of attack or attained objective can put such a massive nation, industry and people out of the game no matter how much materiel is destroyed or relocated or manpower lost. This also demonstrates why strategic bombing, destruction of physical assets (or even a nuclear attack) without more cannot defeat a nation in a total war.
Moscow falls, symbolic victory etc. lets for the sake of argument presume that Stalingrad fell, now its 1942 and the German’s “won” at a massive cost in lives and materiel, and critically, time, and they still have many more such pyrrhic “victories” left to fight, attempting to hold and pacify such a gigantic nation. Even if theyâ€d kept Von Paulusâ€ Army, the armor, air and men were totally exhausted and its hard to imagine a cakewalk victory over any one of these theatres, much less all of them. Without replacing the leadership that kept driving these pyrrhic and unsustainable effortsâ€¦how can we imagine a different set of outcomes?
I don’t think the USSR or other Allies would have sought a peace, because there was no hope of constraining Germany to any borders or conditions by such a peace, and no way to enforce it without Germany first defeating itself through attrition.
I donâ€t think war would not have ended there, ts equally plausible that even after 2 or even 10 such “victories” (and there were many victories) that there would be 10 more required to disintegrate the Soviet Union. In fact, the national defense of the USSR seems to have solidified its philosophical conception, unified it, killed off a lot of potential opposition (in multiple ways) and probably empowered it quite a bit by focusing it on external, rather than internal strife.
The idea that Japan could have effectively invaded the Soviet Union seems implausible. 1) there was nothing of economic or strategic interest in that area at that time for over a thousand miles west, endless untapped wilderness 2) Japanese power projection away from the sea and mechanization were deeply wanting whereas the Soviets had heaps of well-suited irregular troops and a sweet new railroad leading right to the front 3) all Japan’s efforts were long term tied up by a huge, endless intervention in the most populous nation on earth and could not be redirected without major consequences (loss of manchuquo, former UK areas) 4) Japan had looked from sea to land, land to sea, back and forth until they were defeated everywhere 5) both the USSR and USA dwarf Japan in terms of economic power and projection and those were all new all-in enemies for 1941.
Even if they’d been foolish enough to attack, it still may have done little to affect the Russian economy, as they could simply scorch earth and hide behind literally thousands of miles of tundra and boreal forest without any roads.
One last thing to mention is that the Axisâ€ and their leadership had great contempt for Russia and the United States, considering them weak and not unified. This belief was a major undoing, as the conduct of the actual war did not support this view, at all.