Interviewing really is a distinct skill from contributing and the more people crank it the more it seems to test for interview ability.

IQ tests are also distinct skills but IQ scores are the most quantifiable and studied numbers in all of psychology and correlate with all kinds of things like job performance.

I think the purpose of the interview is the same thing. Even though there's no strong evidence for a correlation it's reasonable to believe intuitively that there is.

I suspect (and have seen some evidence) that the interviews he aced were algo-based. Doing well in these is very repeatable, with low additional effort. Behavioural are much harder to do at scale.