I think I kind of understand why the Soviets were able to industrialize that fast and win an existential war against the mighty Wehrmacht.
The so called purges from late 20s to to the 30s were Stalin eliminating these 5th columnists.
The Wehrmacht lost because numbers kind of matter in war. When you look at the natural resources Russia had, the population disparity between Russia and Germany, and the size of territory the Germans attempted to conquer, it really wasn't a close contest at all.
The entire concept of a 5th column is just fear-mongering by most countries who faced defeat due to their incompetence. And the term was used by countries to impose draconian controls and oppression.