Milgram believed that the idea of the agentic state best explained findings, other possibilities were ignored.
One common belief is that he had detected signs of cruelty among his pt, who used the situation to express this. This belief was given substance from the Standford prison experiment as the guards, after a few days, inflicted cruelty on the prisoners despite the fact there was no authority figure telling them to do so.
This suggests that, for some, obedience may be due to agentic shift, but others it may be for the desire to harm others.