On the other hand, while I know nothing about Soumith, he clearly has enough financial runway (see my calc below) to not have to work again.

As far as I know, we all get one life. If one can help it (modulo other constraints), one should not get trapped by prestige, achievement, short-term admiration by others, impact and external facing factors. To see an alternate reality, it helps to escape the bubble, for example, by spending time in a completely different culture or environment where no one knows or cares about what one did.

I admire people taking such decisions. It's easy to be on autopilot in life. But, people who wear their success lightly are rare but more philosophically aware, in my opinion at least. I wish him good luck!