> Why couldn't the Pokemon Wikipedia articles be as extensive as the Bulbapedia ones? There is demonstrable demand and interest in maintaining such extensive information as evidenced by the commitment of the contributors to Bulbapedia to keep it so up to date and pristine.

Cynically, because if all of this popular high-traffic content were on Wikipedia instead of Wikia, it wouldn't deliver ad views.

Jimmy Wales runs both, and the editorial policy just happened to shake out such that his non-profit pushed a ton of high-traffic content onto his for-profit service. Go figure.