Never underestimate the influence of narcissism in hiring, manifested as the kind of blink decision you describe. Teams in a large company develop a personality and culture that more often than not extends to attributes that have less to do with skill and competence and more to do with similarity of physical characteristics and outside interests. (The degenerate case is flat out nepotism, but the more typical case is a team of people fitting a core profile--5'10" 30-something males from second tier colleges, or taller-than-average mustachioed conservatives.)

Most large company hiring practices are not so much a selection of specific traits as they are a filter for ensuring a lack of negative traits. When you factor in the bias of narcissism in interviewers, you'll get competent people who are skillful at reflecting the interviewers' traits back at them (such as the author, who didn't demonstrate incompetency with his first answer, but aced the interview by reflecting the cleverness the interviewer must have self-identified with as "Google material".) After a certain point, four or seven or nine layers of interview will certainly guarantee the incompetent ones don't get through, but at the same time it will also select for the kind of highly adaptable social personality that is often found in political operators.