I don't think they knew for certainty that it would draw better, sure 5th show on FOX did better than the 4th one so they might have thought it's starting to pick-up. Though, I think what gives/gave them the reason to charge more is the demographics. It's mostly young(er) people watching MMA and the advertizers (especially movies, video games etc.) are always looking for shows that attract people around 18-35/45. With no NFL game and I guess no college football either, it was pretty much guaranteed that the show would kill in ratings in that specific demo.