That's a great stat as long as you don't take into account the fact that some NFL Network-only games were also broadcast on network television last year, or that ratings don't take into account games streamed on the internet, or that there was this little hurricane that hit during week 1, or that a Thursday night game featuring San Francisco (the team that started all of this) was up almost 40% over ratings from the same week last year.
Or that in a J.D. Power poll of 9,200 people that attended a professional sporting event in 2016 (roughly half of Neilson's sampling) only 12% said they watched fewer NFL games while 27% said they watched more games, and that only 3% of all respondents said they watched fewer games because of anthem protests while 5.6% said either domestic violence or too many delays and another 2% because of too many commercials.
Or many of a thousand other reasons that there is a decline in ratings.
But yeah, I'm pretty sure that finding the reasoning behind a trend from a 0.01% sample is pretty easy. Especially when that proposed reason lines up with your own opinions.
Edit: Not directed toward you, but more toward people that try and point to any singular reason for the decline in ratings.