He don't want to. And maybe don't want/need to earn more. And that is completely fine. But his impact is huuuge. I'd wish more people did like him. But I don't think many will, because those skilled enough to make something similar would rather work for a higher salary.
So it's more a sigh from me, that I'd wish more people would be able to sustain making and giving away something great like this, without having to sacrifice money. Why should optimizing ad clicks give you millions, but making this only thousands?
You know, in the same way there often are discussions here about making open source income viable. It would be better for everyone if these unsung heroes got more than just praise. Then others would follow suit.
AFAIK, he is French, so you need to compare it with the local job market: there's no way he could get twice as much even in the most-paying company here, the market price for such a profile is probably around €70k, assuming he wanted to work in Paris[1] (or maybe Lille or Lyon), and if he lives anywhere else in France, he's probably already earning as much as he could wish, and he's working one something that matters to him. I would totally take such a deal.
[1] Ok, this is probably way less relevant nowadays, since covid made remote work mainstream for most of us, but remote work was barely imaginable in most French company before the pandemic came.
But people get distracted by things they “can afford,” the amount of money they “need” ratchets way up, and they find themselves missing out on things and making compromises anyway.
If you have already found a thing or two that makes you happy, you don’t need to hedge so much. You don’t have to keep trying to stuff things into a hole in your chest trying to fill it up.
Many, many of my parents’ problems went away when one of them started making over $50k a year. If they had been more content then it would have solved many more. Adjusted for inflation that’s a bit more than $58K today, but if your spouse is doing well enough, that’s still perfectly workable. If your health holds.
This is probably the root of most of tech's angst: people thinking they're entitled to get rich just because they made /run something.
If you can live comfortably doing something as rewarding as making something like Lichess, what more can you really want? People are talking about FU money/financial independence, which I agree is nice, but you can totally get there on $58k/year by living below your means and investing.
The reason I say it leads to angst is when you expect more than a comfortable salary, you're imposing a higher financial burden on the overall system than necessary, which can sometimes work in the short term, but in the long term introduces drag on development/stability because those extra thousands you're personally socking away aren't going towards, say, getting a contractor to address little issues or going into the rainy day fund.