What was the strategic advantage of allowing the germans to invade the soviet union?

The German army (the Wehrmacht) was very unprepared when it came to the Russian weather. They unwisely chose to invade in the middle of the year, and by October time, many of the Germans fighting on the eastern front were suffering in the conditions. They were eventually supplied, but very poorly, with hardly any uniforms and clothing and provisions that would help them survive in the conditions. Because of this, it was strategic to allow the Germans to advance into the Soviet Union, because the army would be exhausted and their morale would be low by the time the Soviet Red Army met them on the battlefield.