I think Hitler was driven by ego in a way. If the Wehrmacht had captured the city that bore the name of his enemy for Hitler it would have been almost like having captured Stalin himself. And it would also have had a tremendously demoralizing effect on the Red Army and the Russian people. Most Americans when they think of World War Two tend to not realize just how pivotal the battle was in the over all strategy of winning the war. The Allies felt that if Hitler had captured Moscow and or Stalingrad they were willing to write the Soviet Union off and sue for peace. Oddly enough today marks 70 years the battle ended.
Hitler was an idiot for not invading the USSR earlier in the year, and for giving Communists the one thing they've never had before or since- the Moral High Ground.
Hitler defenders say that the USSR would've invaded in summer of 1942....you ever see Soviet soldiers perform well outside of the USSR? If the USSR invaded, Hitler's Wehrmacht would've been able to easily defeat them in a defense and counterattack battle.
The only reason the Soviet troops defeated Germany was because they were full of revenge and vodka.