Bet on the “lightning war”.
For a successful blitzkrieg, 3 components are needed:
Numerical superiority, so that the losses do not slow the advance;
Technical and professional superiority, so that these same losses would not be too great;
Relatively small territory so that troops are not depleted during the offensive.
During the war in Europe, all points were respected. But during the invasion of the USSR, the territory turned out to be impressive, and the Germans did not have significant numerical superiority, and over time they were completely outnumbered. Only one component has survived – technical superiority, but only for the first time.
Excessive self-confidence of command
A series of successful wars in Europe inspired the German command, even at the highest level, that they were invincible.
Of course, there were those who sensibly evaluated the power of the Wehrmacht, but their voices sank in the self-confidence of the majority.
In 1941, the Red Army was at the beginning of a large-scale rearmament, which was supposed to be completed by 1944, and was intended to withdraw the USSR army to world leaders.
In 1941, the Red Army was considered backward in terms of equipment. So, for example, Germany hoped to defeat the organized resistance of the Union by August 25th.
In a report dated June 14, 1941, the United Intelligence Committee of the United States (the predecessor of the CIA) completely gave the USSR only 6 weeks in the event of a war with Germany.
In this case, no one took into account two things. The USSR possessed tremendous industrial potential, which could be transferred to military tracks as soon as possible.
In addition, the powerful influence of ideology on the citizens of the Union, who were ready to stand up to the last for their homeland and national characteristics of the country’s population as a whole, was ignored.