Logistics and some idiocy that the whole of the CCCP could be conquered before winter set in. Why Hitler’s generals didn’t put bullets into the heads of NAZI hierarchy is beyond imagination.
Why does America's "hierarchy" continue to draw breath after Viet Nam, Iraq, Afghanistan, Obama, and the 2016 election?
How about the destruction of the Republic due to 50 years of wide-open borders?
Answer:
If you give mediocre people power and status you can get them to do anything. Anything.
It’s quite possible that they could have succeeded if not for Hitler’s meddling and overriding his general staff. By September the army was within striking distance of Moscow with little Soviet forces left between them. And Moscow was the key city. All the railroad and communication systems ran through the city. Probably more than any other nation Russia was dependent on what they called “the center”. Incredibly Hitler called a halt to the advance and sent his panzers hundreds of miles south to help take Kiev. By the time they came back it was November and the Russian roads were a swamp of mud, and winter hit shortly thereafter. It also gave Stalin time to bring a fresh army up from Siberia. Even still the Germans almost got there. They certainly could have taken it in September if Hitler hadn’t squandered the chance. Whether the Soviets could have continued effective resistance without Moscow is doubtful at best.