He has been quite a significant member of a project (Go, or portions there-of, and possible other things I'm not aware of myself) that has impacted people here

He has been quite a significant member of a project (Go, or portions there-of, and possible other things I'm not aware of myself) that has impacted people here through their use of the language, and has affected other languages/frameworks less directly. Leaving Google means he won't be working (at least not directly as he is currently employed to) on that stuff, so the interest is from two angles: what affect might this have on the direction of the projects he is leaving, and what is he moving on to influence next. Me leaving my current job wouldn't make HN because I don't have any such significance. I'd wager the same could be said of almost everybody, but, demonstrably, not him.