It's not just that Norvig is smart; he's specifically skilled at writing really good code, apparently because that's something he cared about and worked on. At JPL I worked with a bunch of smart researchers with PhDs but some wrote better code than others, and it didn't mean they were on a different level intellectually.

Norvig's book _Paradigms of AI Programming_ has 900+ pages presenting code as instructive as that Sudoku solver; I've never seen a better collection. http://norvig.com/paip.html