I am far from alone in this analysis:
Macbeth’s self-justifications were feeble—and his conscience devoured him. Yes, even Iago was a little lamb, too. The imagination and the spiritual strength of Shakespeare’s villains stopped short at a dozen corpses.
Because they had no ideology.
Ideology—that is what gives villainy its long-sought justification and gives the villain the necessary steadfastness and determination…
Thanks to ideology, the twentieth century was fated to experience villainy on a scale calculated in the millions. -- Aleksandr Solzhenitsyn, The Gulag Archipelago
In ideologies there is not Jesus: in this tenderness, his love, his meekness. And ideologies are rigid, always... And when the Christian becomes a disciple of an ideology, he has lost the faith: he is no longer a disciple of Jesus, he is a disciple of this attitude of thought. -- Pope Francis