Apparently, the NBA and other prime-time sports ratings dropped due to the World Series and this Election, as well. Other media experts for all broadcasting have reported that it's not just the NFL, "The TV industry has moved from being mature with broadcast and cable outlets to a startup with all these streaming options." , as well. Like I said, it's a lot more complicated then some originally.
That said, I do agree that much of the NFL's weak numbers could have been helped by putting a better product out there, having enough foresight to know that the Olympics/Election Year/Streaming Technology/Generational Shifting Interests and elongated baseball season could possibly lower viewership this season. They took no initiative, but billions still will be made by the owners, regardless of this.
http://www.sportsmediawatch.com/tag/nba-ratings/
http://www.sportsmediawatch.com/tag/college-football-ratings/
http://www.theverge.com/2016/10/3/13150440/nfl-football-television-viewership-declining
It's Nov. 8th. We'll see where it goes from here.