Probably because the Germans handed Russia's arse to it on a silver platter before it was stopped by the Russian winter and commitments elsewhere.I have, and I have. Who destroyed the most armored divisions? Russia. Who had the highest casualties? Russia. Who had thousands of towns and cities destroyed? Russia. Who single-handedly fought the Eastern Front? Russia.
Russia did not defeat the Germans. The Germans did.
So was England, America, and Japan.Russia was indispensable to the war effort, and you know it.
Actually, Russia relied extensively on western aid in terms of materials for the entire war. Even their vaunted production effort wasn't enough to contain the German advance.
In addition, as has already been stated in posts you obviously hadn't bothered to read or dismssed as being irrelevant, Germany could not commit entirely to Russia while the western allies remained undefeated.
Therefore, the statement that Russia could have won the war single handed is false (or at least not proven to be true), and you have not addressed the op.