I too am often intrigued by the Zimbardo prison study. It is amazing how quickly humans altered their human behavior to match the situation they were placed in. As a study, we can see how this might relate to something like Nazi Germany. We can clearly see how the soldiers, in probably a very short period of time, had to change their behavior to fit the situation that they were placed in. Although it can be difficult at times to draw conclusions from studies that take place in the lab, we can see how this study certainly relates to events that have occurred in our human history. I think the situation is a powerful predictor, but so can the leader like you mentioned in your post.
Thank you for highlighting the importance of keeping participants safe. Can Zimbardo, for example, have kept his participants safe by doing the experiment in a different way?