"It reminds me, in an encouraging way, of the way that German military planners regarded the Soviet Union in the lead-up to Operation Barbarossa. The Slavs are an obviously inferior race; ..."

Ideology played a role, but the data they worked with, was the finnish war, that was disastrous for the sowjet side. Hitler later famously said, it was all a intentionally distraction to make them believe the sowjet army was worth nothing. (Real reasons were more complex, like previous purging).