Obedience is compliance with an order issued by an authority figure.
Obedience is not as general as conformity, it is related to specific instruction from another person.
Milgram proposed the agentic theory: When we act as the agent of someone in authority we find it easy to deny personal responsibility for our actions - just following orders or just doing our job.
Obedience to authority is deeply ingrained from early childhood when we are taught to obey our parents, teachers and elders.
It is possible that the demand characteristics raised obedience rates. In Milgram's experiments people felt they were 'helping' in a scientific experiment. It also helped that the authority appeared to be academic experts at a top university, people would have trusted them.