In this article Stalin's behaviour is argued to be the result of a calculated and fanatical strategy. Stephen Kotkin's book 'Stalin' is referenced, and the suggestion is that criticism of Stalin as insufficiently Communist stems from his political rivals. That in public and private he consistently used Marxist-Leninist language to justify policy, and that ultimately his policies were genuine in principle.
But why would that in itself explain the sheer brutality of his decisions? I would like to know whether there's any evidence to suggest a specific reason for his political violence.
I suspect that being an Old Bolshevik, Stalin never stopped thinking about his country in the paranoid and violent context of the Civil War. Consequently he always considered the existence of the USSR to be perilous, and thought brutal violence was necessary to defend the revolution.
This might also align with his decision to end Lenin's New Economic Plan; and thus return to something more like War Communism. It may also explain why his successors like Krushchev became considerably less brutal, as in their minds the existence of the USSR was a given.
However, I have no evidence to support this idea, and would like to know if any evidence exists to explain the logic behind Stalin's brutality? Why he considered violence on such a scale to be so necessary? Judging by what he actually said on the subject?
All Soviet leaders were Marxist-Leninist Communists, but each one had a different tolerance for violence as a political tool. The question is why Stalin's behaviour was so extreme compared to his successors, and importantly what evidence is there to describe how he justified this?