My offer of an alternate theory: Most of the games in the prime time spots have sucked. I watched MNF this week. I watched about a quarter and a half of the first half. It was a terrible game. It looked worse that those crappy FCS games they have on ESPN later in the season on Wednesday nights. I watched the kickoff Thursday night game btwn the Broncos and Carolina which was an outstanding game. I watched my Chiefs come back and win the following Sunday which was also a good game. Every game I have tried to watch since has been poor. Blowouts and bad play. Along with pissing off your core audience with the kneeling, closed fist stuff, no wonder their ratings are down.
Also the Gangsta-ism of the players has turned off a lot of fans.