Oh yeah, forgot about that lol. Yeah, I think the reason why Adolf Hitler lost the war against Russia and the allies was due to this one infamous battle in operation Barbarossa, the battle of Stalingrad. Hitler mainly focuses his troops on the city because of the massive industries in Stalingrad and because of his ego against stalin.
And I think (Maybe I'm wrong) that Stalingrad was the biggest producer of tanks and weaponry in the soviet union, and hitler wanted that for his advantage in the war against Russia and maybe the allies do to come.
But, the German military underestimated the soviets, some even thinking that the soviets will only carry pitchforks and knives to a gun fight. And let us not forget the harsh Russian winter that the german war machine failed to prepare their soldiers with winter gear.
And most supplies were destroyed or not shipped right away to the soldiers in need.
Hitler even swears to the commander of the forces in Stalingrad that supplies are coming and will be there in no time. But the heavy anti-air defences and the low fuel cause the supply plans to crash or not drop the supplies in the right areas.
To and a middle figure to the problem, Hitler promoted the general of the forces in Stalingrad to field marshal because no field marshal in german history hasn't once surrendered to the enemies their fighting. And most german soldiers were exhausted from fighting and most just gave themselves up to the Russians.
And the german commander (Now field marshal) said f**k Hitler and surrender to the Russians, turning the tide of war for Germany.