Evil loses in the end because it's short-sighted.
Several facts are indisputable:
Hitler's plan to attack the USSR was stupid, insane, and cost him the war.
The various Wehrmacht generals AFAIC fell into three camps-
German patriots who wanted Germany to avenge the wrongs of the treaty of Versailles. eg Rommel, Beck, Canaris
Self-seeking careerists who liked combat and earning their spurs Guderian, Skorzeny, etc.
True Nazis with all the racist baggage.
Membership fluctuated between the camps based on conscience, opportunities, and expediency.
AFAIK under more professional military leadership, the Wehrmacht could have done much better in defending themselves in the Eastern Front, but real professionals wouldn't have invaded Russia a la Barbarossa in 1941 or any other time. A vague scanning of Nappy's Russian campaign using the resources of a united western Europe and still failing would've been instructive, but they thought they had the technology, Aryan will, and so forth to go smash the Bolsheviki once and for all without anyone else's help. To a man the Wehrmacht were all delusional on that score. (No hate on the Italians, Spaniards, Romanians, and others that often fought well on the Eastern front on Germany's side, but they were treated badly, equipped worse, and coordination with OKW was a grim joke from the git-go and never improved.)
Later, the Wehrmacht were hampered not only by Hitler's increasingly crackpot meddling but Himmler's SS and other players who could've cared less about military victory as long as the Final Solution was carried out and the occupation was as brutal and silly as possible. There were pragmatic exceptions, such as Heydrich as well as humane exceptions to a very brutal and self-defeating rule.
Plus let's not forget the logistical muddle the Wehrmacht was in from 1939-1943 while Germany kept trying to wage war on the cheap w/o gearing up for full war production. That was the whole point to blitzkrieg. They wanted to win the war in twelve weeks. Once that wasn't happening, things went downhill, because Germany's economy was in no shape for an ongoing war of attrition with 3/4 of the planet. Even with sane, competent leadership on the battlefield, they had too much wrong elsewhere to make much of a difference in a total war.
Hitler's leadership style was to have self-defeating intramural squabbling between different factions to keep them from developing a consensus to depose him. Giving the generals opportunities for their men to develop competing loyalties to their commanders was anathema to Nazi doctrine.
You didn't swear loyalty to Germany in the Wehrmacht, you swore it to Hitler personally.
Only after five years of war and two years of noticing that there were way too many Soviets, Yanks, Brits, and other folks coming over the hill for them to fight off (and German cities going up in flames) did you see dissension in the ranks.
Listening to Canaris would've been smarter, allowing the captured Soviet POWs to organize into units dedicated to liberating the USSR and establishing non-communist Russia, Ukraine, et al. Allowing them to liberate and rule themselves would've saved the endless drain of resources
partisans inflicted on the German rear. However, you'd need capable, non-ideological pragmatists in charge, not racist loons like Himmler or corrupt kleptomaniacs like Goring in charge of running the civilian economy in occupied territory, but then we wouldn't be talking about Nazis, would we?