I think it has more to do with fans sick of the B.S. changes over the past 15+ years especially the championship format that supposedly rewards race winners. The "car of tomorrow" with it's ground effect kit and wing really put a dent in the fanbase.
I wonder if it has anything to do with the Sponsorship being restricted? ( no more Winston, Marlboro, etc.) I don't really see how that could do it.....but you never know!