What explains the failure of the blitzkrieg of Nazi Germany against the USSR?

This is due to the fact that the German command did not expect such fierce resistance from the Soviet troops. So the plan for the lightning wave was completely failed by the end of 1941. German troops were exhausted, in addition, more than half of the tanks were lost, which played one of the key roles of the further offensive. The very offensive of the German troops stopped near Moscow, and then the Germans were driven back. So the first stage of hostilities ended.