Because Steve Sansweet hired him back in 2000 to get the Star Wars website up and running, and, with all of the stuff he had to winnow through for material to post, even before the formation of the Story Group in '08 people were looking to him for continuity and fact checking. It's been his job for over a decade to essentially know every frame of the films, Clone Wars, and Rebels... but mainly the films. The number of things he and Leland have gotten wrong or didn't know is inexcusable for being experts in their positions.
It's pretty interesting that many of the people here on theRPF know BOTH the lore and production of the films better than some of the people that work at Lucasfilm. I couldn't say with confidence that I am one of them, but still.