They probably just realized that it was a bad idea all around to begin with. It's important to remember that the only possible place to have a knothole was in an existing opening. The seats over the two other large openings, in left center and right center, are too deep to allow fans to get even remotely close. That left the right field corner. I don't know why they thought that would be a good spot for it during games, but there's no real way that anyone could see the action from that angle. At least not the batter. You could see into the stadium, but it's not like fans would be able to actually watch the game like fans in the stadium, on the rooftops, or at home.