Here is an example of a military operation doomed from the start, the Spanish Armada, for comparison.
The Spanish Armada plan was for a fleet that had been built in the previous six years, by a country that had only maintained naval forces in the Mediterranean, to be sent to the Channel and defeat an English fleet that had weapons with greater range. Then an army based in Flanders would cross to England in small boats. For this to work, not only did they need perfect weather when weather forecasting was more unreliable than now, they needed radio to coordinate with the army and navy, so it depended on technology that didn't exist. Note that the Spanish Armada actually came close, the fleet got up the Channel to the appointed rendevous point and the army actually started embarking, and this was an operation that really was technically not possible given the technology at the time.
On the other hand, it was technically feasible for both the German army to take over lots of Russian territories and to cause the Russian government to collapse. We know this because in 1915-18, the German army accomplished both, when most of the German army was in France and Belgium. In 1941 they secured air superiority quickly and could concentrate nearly everything against Russia. So it was unlikely but technically feasible.
However, the key was the Stalinish regime collapsing, and this is where, contrary to conventional wisdom, the purges helped Stalin and the communist government survive. Failing that, the Germans still could have taken over large amounts of Russian territory, cut Russia off from much of its oil supply in the Caucasus, and left a rump communist Russian government as a sort of nuisance.