The first comment on the blog has it.

Subjectively, personally, we can all decide for ourselves what purpose we live for, but the purpose of life as a phenomenon in the world is not to enjoy itself. It's to perpetuate itself. Stay alive long enough and win a competition for scarce resources needed to reproduce. Being largely freed from the tyranny of constant threats and true scarcity, humans can aspire for more, but we're still living creatures. When bears come down from the mountains to fight to the death for winner take all access to the pool of twelve available mates, they're not happy when they win. They mate and get back to it, rest a few months, then fatten up again and prepare for another year of fighting to the death, until they finally get old and lose to a younger, stronger competitor. That's the tale of thousands of generations of ancestors spilled into all of us, humanity included.

Even just look at specific highly successful humans. Take famously miserable, no friends Michael Jordan. Win every year, enjoy it for twenty seconds, then immediately get back to work, 14 hours in the gym every day, alienating everyone you ever meet, having no friends, only to win again and feel just as hollow. Why? Because genes and behaviors that make an animal that driven, to succeed at any and all cost, including their own wellbeing, is the basis of success at the only thing that actually matters to life itself, as opposed to any individual thinking creature.

He may or may not want to be that way. I'm a reasonably smart guy, nowhere near as driven or successful as Michael Jordan, but I still often wish I was less smart and less driven than I am. The logic of life dictates that we always want more. Nothing is ever good enough. It's why we're collectively miserable no matter how much abundance and wealth we collectively create, even among those who have more than 99% of the world. We can tell each other all the stories we want about the fairness of the distribution, convince yourself your misery is especially justified because you believe you'll be the first generation of humans ever to pay more for housing than your parents. It isn't that. You're not special. None of us are. Dissatisfaction and always wanting more are core to what makes life life.

Being smart probably makes you better at life, but being better at life is barely correlated with enjoying it, if at all.