https://aeon.co/ideas/what-did-hannah-arendt-really-mean-by-the-banality-of-evil
he banality-of-evil thesis was a flashpoint for controversy. To Arendt’s critics, it seemed absolutely inexplicable that Eichmann could have played a key role in the Nazi genocide yet have no evil intentions. Gershom Scholem, a fellow philosopher (and theologian), wrote to Arendt in 1963 that her banality-of-evil thesis was merely a slogan that ‘does not impress me, certainly, as the product of profound analysis’. Mary McCarthy, a novelist and good friend of Arendt, voiced sheer incomprehension: ‘[I]t seems to me that what you are saying is that Eichmann lacks an inherent human quality: the capacity for thought, consciousness – conscience. But then isn’t he a monster simply?’
How my heart sings 
Maybe she was afraid that the capacity for great evil is more common in people than we think. It’s horrible to contemplate, because then the worry is that such atrocities could happen again.
Yes indeed that doesn’t worry me now when society seems so unstable