The main thing Hitler could have done, is to treat the Russians humanely, along the lines of in Vichy France.
Many Russians originally greeted the Wehrmacht as Liberators from Stalin.
General Vlasov raised an army to fight alongside the Germans, and he had plenty of volunteers. But Hitler was afraid of allowing the Russians to have arms, even to fight on his side.
Not quite true. The Cossacks were welcomed to fight with the Germans with open arms. By 1942, by now short of men, Hitler was willing to let his Generals make the decision whether to recruit local Russians.
Also, by 1942 and later there were many units of the SS that consisted of enlisted men from the conquered Russian territories, including the Ukraine, Latvia, Lithuania, and Estonia. They fought hard and bravely for the Germans.