I just moved from San Francisco to Nashville, TN last week. For me, it was a combination of the cost of living and lack of family in the area. I'll always miss San Francisco, but our rent has halved, our square footage has doubled, and I no longer pay state income taxes. I'm still doing interesting work (remotely) for the same company, so I can't complain!
Genius is a dynamic thing rendered via the lens of social value.
If scientific progress is our goal, then I would argue that forming cliques around a clique-governed definition of "most likely to elicit genius" is not only wrong, but dangerous. Heuristics can be ugly things.
Also, MENSA reminds me of church. Church is boring.