I think it is because of Fantasy Football. I used to watch every game I could just to soak in the games and see the games. However I do think they oversaturated the market. I don't care about a game itself anymore, just the player in it. (Besides the Bills) I don't have to watch them play now, I can just check the stats on my phone and not need to waste 3 nights (Thrus, Sun, Mon)
I really think that backfired, because now young fans don't cheer for one team anymore, they cheer for players, and the can't even watch them because of their market. They just watch the highlights on social media.
It doesn't help that the qbs in the league are awful except for the top 3 or 4. Nobody wants to watch Tom Savage on a Monday Night. I know I didnt.