The Germans could've took them out. The Germans could've focused all their Military resources on the Eastern Front to capturing Moscow, then taking it from the central position. But Hitler was focused on capturing the oil fields, which was the primary goal on the African theatre. The Germans were so strong they made the Soviets a superpower. Just look at the casualty and production statistics for the Soviets. No one loses 20,000+ Tanks within six months without having an incredible military industry and economy.