Both sides of the experiment (the guards and the prisoners) both felt as if they were playing a role and it became way too real which is why the experiment shut down so quickly. they simply weren't weak people but when they first started this it was like a character. Since they didn't have any connection to the outside world, they felt as if they were becoming the character they were playing. One prisoner did have power over the situation and asked to leave (not quite sure if he did actually leave, but i think he did end up staying cause he genuinely felt that the other prisoners would turn on him and he would get more punishments from the guards).
