Exactly. Capture or destroy the major cities and the oilfields. Most of the USSR was uninhabited, so you didn't need to conquer it all, just the bits that mattered.
I agree that Stalin was just as ruthless as Hitler, but if he'd lost his main supplies of fuel and munitions there wouldn't have been a lot he could have done other than carry out guerilla raids.
In my opinion Germany's intention wasn't to conquer Russia; in fact if Hitler had thought Stalin trustworthy he wouldn't have invaded at all. But he knew that given time, Russia would have attacked him, so he was just getting there first.
1937 Stalin had purged the Soviet army of any Generals and officers who might be a potential threat to him. he in effect weakened his army. That and the difficulty that The Soviets had against Finland's Much smaller army convince Hitler that the Soviet Union would fall over like a house of cards.