Hitler attacked Russia for many reasons. Exploitation of it's resources by force rather than having to trade for them was one. Hitler would have believed they could be exploited fast as food from the Ukraine and oil from Baku could have been flowing pretty soon. At least Hitler, who remember was banking on a Soviet collapse, would have believed so and it's his beliefs that matter in looking at his reasons for his invasion. A second reason for invasion is the removing of a potential future threat to Germany because even if Hitler had contempt for the Soviet military in the short term he must have feared that over time they could learn from the Finland debacle and improve. Also if America joined the war in the west after a year or two and Germany was ultimately under pressure there say in 1943 or 44 what was to stop Stalin from then earning the gratitude of the West and joining in the war, and after having had years for improved training and preparation of his forces. Germany would then be in a two front war and at the time of Stalin's choosing. Completely and as Hitler believed rapidly removing such a future disastrous possibility while at the same time guaranteeing German food and oil needs for a long conflict with the West must have seemed an obvious course of action for Hitler. Then there's also the timing. In 1941 Britain was weak, not capable of invading France. Russia was, at least for the moment, militarily incompetent as far as the Finland war had shown. And America while supplying Britain was only starting it's own rearmament. It all adds up to giving Germany, if it could prepare an assault force, an obvious window of opportunity to get rid of Russia.