From what I understand, the Nazis believed that an Aryan nation was made up of superior genetics and it was "inevitable" that Aryans would one day rule the world because of their prowess.
So when the Soviets started thumping the German military in battle after battle (especially from 1942 onwards), how did the Nazi propaganda mill explain this to its population? Wouldn't German losses require admitting that somehow, even the supposed untermenschen seemed to be doing something right - even better - than the Master Race?
I feel like this time around there are no scapegoats; they couldn't blame it on the Jews, considering that there were no free Jews left by 1942.
Hitler blamed those loses on the "cowardice" of his commanders. He believed that the failure at Moscow and Stalingrad was the direct result of German commanders being too weak-minded. Obviously, he was dead wrong. Still, this always resulted in mass layoffs across the senior officer cadre. I don't know precisely how the Propaganda Ministry that was ran by Joseph Goebbels presented those two defeats. I do know in another case – i.e. for Operation Citadel – the ministry presented the mighty German offensive as a local raid into enemy flanks because the High Command had some reservations for the prospects of the offensive.
Operation Citadel resulted in the Battle of Kursk, and the battle was ultimately a loss for the Germans (even though they incurred less casualties). The situation on the ground at Kursk, and pressing developments in other parts of Europe, forced Hitler to halt the offensive; and just like that it became a loss and a huge waste of bloody effort. In fact, it was the last strategic offensive Germany carried out in the Eastern Front.
The complete defeat of the German Army Group in 1944 (during the Soviet Operation Bagration) was followed up with a fanatic call to defend the fatherland – Germany. There was no more room for cover-ups and funny rhetoric. This time around, the Propaganda Ministry worked overtime to present the invading Soviets as a Slavic horde of inhuman barbarians, and unfortunately the mass rapes in Prussia in January 1945 only reinforced that image.