I think a lot of comic book fans are a impatient bunch by and large, and seemingly very quick to jump the gun and assume the worst if someone puts out one bad story.
Although sometimes they are right..(Witness the awesome plunge in qulaity that is Frank Miller's writing. And boy does it pain me to admit that. As I loved the guys work back in the 80es)
But as far as this is concerned, I've heard though that this series was initially intended to be an ongoing book, but something went wrong in editorial mandates and the like and so it's now turned into a mini. So maybe Robinson's heart just isn't in it anymore. It really could be that simple..