I am currently reading a memoir by Stuka ace Hans Ulrich Rudel and he notes that the soviet capacity to replace rearm was uncanny and even how dismayed he would be seeing new tank formations day after day despite his squadron destroying so many , so was soviet superiors in manpower and industry simply too great and OB was innately flawed because of this
/u/Rob-With-One-B answered part of this answer previously when stating that the German Army failed due to logistical reasons.
/u/dandan_noodles touched on your question in particular stating that the Germans failed to take into account the Soviet's reserve personnel.
Hopefully we get a direct answer to your question soon. Don't forget to check the FAQ section in this sub as well as using the Search feature.
Quick follow on - Antony Beevor notes that "had the threat in Khalin Ghol not been eliminated and Siberian divisions not withdrawn when the Red Army was at its most vulnerable , the outcome of the secound world war may have been very different" - what extent do you agree?