It's a good question, but the answer might be quite a simple one: Their boss seems to be an artificial intelligence. In this case predicting the behavior of psychologically challenged personnel could be easier than perfectly healthy ones. Normal people could start to second-guess all the terror and mass murders they are spreading around but people with certified problems can go forward with single-minded determination till the very end and never look back. As long as the AI complies to some basic, individual requirements such weirdos might have.

It's all about control, and while superficially thinking controlling madmen might seem more challenging than sane people, it's not necessarily so if you are able to provide the madmen with what they crave.