I think the matchups certainly have something to do with it. There is also something to the fact that many people just don't watch from home anymore. As more and more homes cut the cord from cable, the Sunday Ticket package is picked up less and less. People just choose to go to the local sports bar instead. That doesn't register correctly in the ratings. The weather at this time of year has also been warmer/better than normal in many parts of the country...so people may just choose to be outdoors in the evenings before it starts to get too cold to do so.

I also think the hyping of betting/fantasy sports is a double edged sword. Yeah, it draws interest for those with a "stake" in games and would seem to drive MORE interest...but only until someone's wager is toast for the week and they lose interest in even casually watching anymore. If they have a bad day in fantasy/gambling, they may just skip tuning into the prime time game even if they probably would have otherwise.