It was a combination of things for me; being a huge baseball card/stat nerd in my younger days made it kind of a natural progression. It helped having friends over the years that were HUGE into old school fantasy baseball, so they explained a lot of this to me while I just had a dazed look on my face. A cousin introduced me to Bill James' ideas in the late 90's, too. Like many others here, Moneyball just sort of crystalized these various ideas a as a real, legitimate and awesome "thing," and I remember going into the 2004 season just not getting enough of it. That said, I still consider my overall stat/sabermetric knowledge pretty limited. Math is not a strong suit for me at all, so I constantly rely on reading over other people's analysis and definitions/glossaries to remind me just what the hell I'm looking at.