When interviewing civil servants, the examiner told the candidates not to be nervous. Why do candidates still fail the exam because of nervousness?

Because the interview is a group of people around the candidates to score their comprehensive quality, nervousness is human nature, depending on each candidate's ability to handle the situation on the spot.

Some candidates can control their nervousness in time and complete the interview at a high level, so their scores will be correspondingly higher. Some candidates can't control their high level, because the admission is proportional, and it is reasonable for their scores to be lower than others.