I hope I don’t come off as somewhat naive.
I noticed during my times of maturing when i was around 17 I started to become indifferent to more and more things. I’ve seen this with a lot of people too, my mother who I can say wasn’t the brightest of people went through the same over a year’s time in which I simply talked to her about the history of religion, reality of politics, the illusion of freewill( ) and much more.
““Happiness in intelligent people is the rarest thing I know.” -Ernest Hemingway
IMO what you’re referring to are people who are intelligent enough not to live by illusions but not intelligent enough to see how things can be better or even the good around them.
Really stupid people are also unhappy since they so frequently misjudge reality and bear the consequences. Some people are happy becuae they’re not that stupid, but are not smart enough to see through comforting fairy tales. Then there’s the people you’re describing. But really smart people are good at being alive in the world and allowing themselves to engage and feel alive and effective. This is all supposing that nothing else is at work which is of course never the case.
I recently saw the movie The Hurt Locker. (I recommend watching it, ignore the chris hedges quote at the beginning though. Sure its a bit larger/abusrder than life, but as a movie it is well done about an EOD team in iraq)
In the movie, there’s a sequence where a father talks to an infant son. A one way conversation goes on about how, when an infant, you love many many things, toys, etc. As you grow up, you end up loving one or maybe two things total.
I think the moral here is that as you grow up and learn and mature, you get tired of many things, some of them you get tired of quickly, some of them slowly; but you do get tired of very many things and stop caring about them.
A corollary for me about this is, if we could truly be immortal, what could you possibly care about when you are 10,000 years old? When you are 10,000,000 years old? Is it even possible to be that old, and to retain anything of your personality from when you ever 100 years old?
Also, in simple terms of being sad or happy, I don’t think intelligence or maturity is a factor here. Its a factor in overall wisdom and being selective about what you care about, but plain happiness can be easily achieved even in the most advanced stages of wisdom by using meditation.
Happiness lies in learning how to arrange your expectations so they’re not continuously being disappointed.
Arthur Schopenhauer: “The more intelligent you are, the more knowledgeable you become, the more you increase your sorrow.”
This sadness is due to seeing the world for what it is, in some basic and harsh realities, example, life lives upon life. The very nature of sorrow I believe is temporality, the human condition as, a creature for a day. “Those who know the most, must mourn the deepest Orr the fatal truth, the tree of knowledge is not that of life.” Byron