He lost interest, no.
He was probably still interested in the job but for some reason during the interview he just found that he was having trouble concentrating on what he was meant to be doing (answering the questions intelligently and eloquently). He might have been distracted by other thoughts going through his mind. Perhaps he starts answering a question perfectly well but during the course of his answer he drifted off the topic instead of focusing on what he had actually been asked.
Interested in Language