I haven't been through the whole thread yet, but I wouldn't use Monday night as a good metric. More and more people are "cutting the cable". With Netflix, Amazon Prime, and Hulu there is enough content to keep even the most avid TV watcher busy, and the cost is minimal. Cable TV has always been a bad deal, people just paid it cuz there was nothing else. I sat there while my In-Laws signed up to pay close to $200 for cable TV per month, insanity!
Also everyone hates ESPN these days due to them deciding they are some political news outlet. So if ESPN was keeping you on the cable, it isn't anymore.
Also the more ready access to Thursday Night football due to it being on Prime doesn't help Monday either. You can now watch three games on Sunday, one on Monday, one on Thursday, and sometimes 4 on Sunday if they have an early game in London that is televised. That is a shit ton of football! I watch enough between Thursday and Sunday that I don't really care if I can't watch Monday.
It is possible that all of the social issues may have an affect on the NFL, but I wouldn't use Monday as a good metric of that. Streaming and distaste for ESPN are doing more to torpedo that.