Stephen Kotkin (briefly referenced in the article) is a history professor at Princeton University and known as the leading Stalin scholar. He's written amazing books and has long interviews on the subject on youtube. One thing that stood out from his talks/books is that he proposes that Stalin was no a psychopathic killer (unlike many other biographers/scholars) but a person who genuinely and deeply believed in communism and was willing to sacrifice anything and everything for it. He also describes Stalin as a super hard-working and pretty smart person.

Disclaimer: Kotkin is absolutely NOT a fan of Stalin, just trying to be thorough and impartial.