1. Happiness is an emotion governed by feedback loops in the body and brain. This is useful to keep us alive, and motivated by staying that way by planning, procreating, eating dense calories, etc... and has evolved to be tightly regulated. Why would this have evolved to be different for any defining features (bigger muscles, more stamina, faster mental logic)?

2. We take joy from what we do well; we enjoy doing what we do well with others; and we self-select for life partners who we enjoy spending time with, which often includes some similarities, for example:

- being able to enjoy downhill skiing for a whole day together and going out for drinks and dancing afterwards - enjoying calm country lifestyles vs city bustle - being a BP beautiful person who likes to live it up at parties ... being a smart person who can work meaningfully on hard problems (and who occasionally should check their ego while they do)

The better you are at something and the further you want to take it personally (often to the enjoyment and encouragement of others, and to the sacrifice of those who spend their lives with you unless they are in similar straits), the harder it is to find people that match (including for dating/partnership prospects). The more average (or less selective) you are (whether deliberately or not), the more people there are that will fit criteria which make you feel more fulfilment.

In the case of smarts, where it is reinforced through decades of schooling to be a large advantage, it can also carry a lot of unpleasant real-world baggage.

- others may envy you - others may give up early assuming you can easily best them - others may consciously decide to cheat to keep up with you - others may not always enjoy your company (when it cramps on their personal sense of mastery/autonomy/purpose) - since your ideas are often logical/beneficial, others may more frequently hear your ideas, internalize them, and (consciously or unconsciously) later act on them without ever thinking to re-involve you or say thank you (or that maybe if that one idea that someone turned into a company had some kickback to you, your logical/beneficial ideas could reach more people).

I'd imagine this gets worse the farther out you are on the bell-curve and could distort personal beliefs (whether reasoned/real from that big brain or reactive/comforting to avoid future pain) through negative reinforcement. It can also lead people to hide their intelligence to fit in, or decide to reach for different kinds of satisfaction other than what we might think they would be capable of. A lot of this is true for other aptitudes too, though more pronounced for those which are of greater perceived importance.

But hey, that's why it's the pursuit of happiness, right?