You're leaving out a number of salient facts:The Mosin, however did win WWII, as the other allies would not have been able to take Germany without their help. If the Germans full force had been on the western front, I am sure we would've been speaking German or Japanese.
People underestimate how close we were in WWI and II to losing, at several points our then antiquated military techniques cost thousands of lives and we were in such deadlocks that through attrition, the Germans had a good chance of defeating us. The Achilles heel of Germany in WWI was that they relied too much on the Allies delay in adapting to the trench warfare, in WWII it was Hitler sabotaging weapons development, had weapons like the MP44 and FG42 and so on had been more heavily fielded, we would have been devastated.
Enough with the aside.
1) The Russians supplied ZERO of their own locomotive power during the war. Every locomotive put into service after hostilities commenced with Germany came to them from Lend Lease. I make this my #1 point because the only way the Russians survived was by moving their entire industrial base east to escape German bombing - BY RAIL.
2) The Russians invested ZERO resources into strategic bombing. All of this came from the US and Great Britain. Had the US and Great Britain not launched sustained and massively costly day and night bombing campaigns against German industry, there is little doubt in my mind the war would have turned out completely differently. Allied bombings of German synthfuels plants crippled both the Wehrmacht and Luftwaffe and made launching attacks quite difficult and time-consuming.
3) The Russians accepted vast amounts of warmaking materiel and supplies from the western Allies via lend lease. The Russians would never have survived without this assistance.
What the Russians DID do, was correctly calculate that they had the means and resolve to throw more of their own citizens (both combatants and noncombatants alike) into the meatgrinder than the Germans did. Whether this is a morally acceptable act is up to the individual to determine on his or her own; however it is not really open to debate.