It really is helpful, socially, to assume good intent. It avoids unnecessary arguments (/wars). Additionally, if you spend a little time digging in when you have assumed bad intent, you'll almost always find that the person has good intent, there has just been a misunderstanding, or miscommunication, or they face very different incentives or have a different set of underlying assumptions.

As for megalomania - it's likely we live in different locations/and or work in different industries. Where I am, interviewers don't hold the power. Candidates do. Especially candidates who are judged to be good. Good candidates make a judgement call as to where they want to work because they have many options. They exercise said power, negotiate higher salaries, and leave if they don't like the arrangement. And good for them, they have in demand skills and a good attitude.

I understand it isn't like this in all locations/industries.