I doubt that biographical details about Stalin's erudition and connection to his political actions generalize. It's entirely possible for a well-read dictator to perform quite admirably. Take, for example, Pedro II of Brazil. He was the closest I've ever encountered to the Platonic ideal of the philosopher-king.

World leaders are highly idiosyncratic people, I think. Taking empirical psychological results that apply to general populations (more likely Western college students in practice) and expecting prominent historical figures to conform to them is a mistaken approach.