I think the question only makes sense if you have already a completely diminished view of what a human person is to begin with. In any earlier century the answer would have been very obvious. Humans are oriented towards the infinite, beauty, truth, goodness and being smart doesn't get you there any more than being rich or tall.

In a practical sense maybe you're a bit happier if you're smart for the same reason you're a bit happier if you're handsome but obviously this does not at all address any question of meaning beyond the horizon of everyday problems.

This whole framing in the article, that smart people ought to be happier because they have an easier time solving problems is hilarious. That's works for a Roomba, it doesn't work for a person.