They should have driven south and cut Russia off from her oil and grain supplies (and gained them for themselves)They did try to do this as well as pushing towards Moscow and up towards Leningrad. Wouldn't focusing South have left the rest of mechanized Soviet Union poised on the border? Worth noting that when Barbarossa began the Soviet Union was second only to the USA in industrialization and was already highly militarized.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
