As everything else in life its priority and effort mixed in with a bit of affinity. Not everyone want to put in the effort and time to become top tier in their profession: those who do obviously become better than those who don't.
Consider what happens if the project being hired for is unexpectedly canceled soon after hiring. Or internal politics and personality conflicts end up being an issue. It doesn't take much turnover at all to completely change the dynamics of a team, regardless of whether or not all the replacements are equally skilled.
Teams are complex systems. Such mental shortcuts provide a false sense of knowledge (and usually superiority) for those who otherwise fail to understand the logistic and social complexities involved. Real life isn't an RPG with a level system; the fact that this even needs to be pointed out to otherwise intelligent and well educated people is outrageous.
I can't tell the elite 5% programmers from the 70%+ percentile programmers, or what ever numbers I make up, during the interview process anyway. It's maybe possible to spot rock buttom programmers from the best, but telling a mediocre programmer (50th percentile) from a really bad is probably really hard.
Interviewing resembles dating. Spam untill you suceed if you cant be picky.