Ulam was very famous (at least among nerds) and extremely impactful on the real world, maybe not entirely in a good way (keywords: "Teller Ulam"). The book was very good. I didn't know til just now that there was a movie. I read the book quite a few years ago so when I saw the headline, I tried to remember what unsung scientist(s) Ulam might have written about in it, that would help us remember them. Imagine my surprise on clicking the link, that the unsung scientist was Ulam himself. Ulam was great, but quite well known, even if there aren't any literal songs about him.

Added: I can only think of one really "sung" mathematician: https://www.youtube.com/watch?v=_lf1mB8OZeg