The Germans suffered enormous difficulties in just getting where they needed to get. For example, some mention was made previously about poor decisions made by Hitler that led to the derailing of the 1941 offensive. Certainlly Hitler was no Napoleon, and he made a lot of mistakes, but not all of the failure of the '41 campaign can be laid at his feet. A popular myth is the decision to send guderains armour south after Smolensk. In fact the decision was made because of reports received from Von Bock, and others about a number of problems at the front. The Infantry had suffered badly during Smolensk, and was down to about 40% rifle strength. It needed time to recover, according to Von Bock, and backed up by Halder (read his diary). The wheeled transport in the Infantry formations wheeled transport, which contained the majority of the French trucks being used by the Wehrmacht was in a porr state of repair, meaning that the distance from the railheads and the overall mobility of the infantry had been reduced markedly since the start of the campaign. The railheads were stuck at Minsk, and would take 6 weeks to advance to Smolensk, the front asa at the end of July. There was nothing anybody could do about that, because the initial planning had envisaged a full soviet collapse by the time of the fall of Minsk. There were simply not the raw materials available to increase the rate of repair after the railheads had reached Minsk. Nor was there the engineering support to make it go faaster. Bock requested, and got, six weeks, in which to refit the Infantry of AGC.
The armour of the Heersgruppe was in relatively good condition. OKH was worried about the activities of isolated Soviet elements in the pripet, and also the lagging progress of AGS who had been held up by a combination of stiffer than expected Soviet resistance, and some localised flooding of the Dnieper. On trecommendation that it was better to do something, rather than nothing, again from OKH, Hitler opted to try and kill two birds with the one stone, by assisting the progress of AGS by shifting the MLA of the armour from Moscow, to Kiev. OKH had durther advised that whilst 2nd abnd 3rd Panzer Gruppes might be able to push onto Moscow, given the weak resistance now in front of AGC following Smolensk, there were strong resrves being readied behind Moscow and a strong likelihood that the German armour would be encircled, and /or suffer enormous casualties. Faced with assessment that were being presented to him at the time, it is hard not agree with Hitlers decision not to divert the armour.
This is just one example of the litany of circumstances that make the argument that the germans could "take out" the Russians a total furphy, at least in the single summer campaign. OKHs original assessment that it would take at least two summers, and probably three, and that was on the basis of weak Soviet resistance. as it happened, Soviet resistance was anything but weak