What separates a good interviewer from a bad one?

Making an effort to find interesting things about the interviewee.

I'm not sure if you mean like Lex Fridman or for a job but that applies to both.

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Recently, Lex interviewed Rick Rubin and sometimes you can't tell who's the interviewer. And here's Rick interviewing Pharell, notice how peculiar his questions are:

https://www.youtube.com/watch?v=PnahkJevp64