Agree -- but this group had a few outstanding characteristics, IMO. These were not hard-charging high achievers who made plans to kill between big deals and tennis dates. Several were vulnerable due to circumstances of family, physical and/ or mental health, financial dependence, etc. All were conditioned to be strong in faith and/ or ideism -- and were open to prophetic visions as presumptive evidence for the importance of continued and even enhanced levels of faith.
They believed in spiritual warfare, and in their own powers to compete in it, despite what some (like myself) regard as almost comic-book level reaches in this regard. And these beliefs were in some ways compensatory -- ZP believing she had a gift of controlling weather despite very limited power IRL; LV's pride in being a world-conquering goddess despite her very limited achievements professionally and personal unhappiness. It was an RPG that became real life.
Once you have faith in a leader -- I hesitate to say "charismatic" -- like CD, and buy into that view of the world as light and dark and in his ability to discern the workings of evil on earth and to devise ways of defeating it, then depersonalizing children and men to the degree they were able to, plus an initially willing accomplice in AC, plus whatever basic coldheartedness helps make a CD or LV, makes it possible to commit murder in the ways they did.
These were monstrous crimes. But they aren't without precedent. Part of me thinks it's the rank ordinariness of CD's followers that makes this seem so horrific and new -- churchy, mostly middle-class, family oriented (hah!), and mostly white. They might help out at a church sale -- and then compare notes on who was light/ dark and marked for murder.
Bog-standard folk, who can do the things they did, then go dance on a beach in Hawaii. And then come home. And find others. Maybe that's the horror.
And even now, many of this crew still believe.