They somewhere along the road adapted a new faith rather than their traditional faith.
The new faith is called "The Perfectability of the Human Condition: Creating Heaven on Earth".
They for the most part don't see their thoughts and actions as evil--but neither did the followers of Hitler believe their thoughts and actions were evil.
Authoress Hannah Arendt coined the term "the banality of evil".
And the worst part of it, is that they fail to realize that it is they, themselves, who must be eliminated entirely by their fellow believers in order for the "New Age" to dawn.
The events of the Holocaust destroyed too many Jews' faith and belief in a Higher Power who loves them and has a Covenant with them.
Not that this is an excuse for all of them, but many good people lost their belief in anything save physically surviving on their own for just one more day.