Psychology behind dumb child doing good in academics
Most people confuse shyness with introversion, and the difference is that shy people do it out of fear, while introverted people do it out of the urge to be alone.

Being shy is a bad thing.

Being an introvert is NOT a bad thing.

People also confuse Dumbness with Gullibility.

Gullibility is a failure of social intelligence, which is again a clear sign of high introversion, and they do that because they're a better judge of character.

Simply put "Intelligent people are more likely to trust others, while those who score lower on measures of intelligence are less likely to do so"

I couldn't do better than this.

source:

https://www.sciencedaily.com/releases/2014/03/140316133840.htm