Why do you think the 6 smartest countries in the world are all from East Asia?

My theory is, they have affordable sea food because of their close location to water, and most of these countries have variations between hot and cold weather and I believe contrast boosts I. Q. Too much contrast might decrease I. Q. which might be why countries with extreme weather changes throughout the year are not in the top 10.

Why do you think the 6 smartest countries in the world are all from East Asia?
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