Even granted a D-coord change and loss of a key DT, how could the 13-3 Titans of last year turn around this year and set a 30 year record with an epic 59-0 loss to the Patriots. With -7 passing yards to boot!
The only answer is that they mailed it in. I see two ways that happens. First, the Titans have given up on the season and have no confidence in coaching staff or team management, and just didn't have the heart to play. Second, they wanted to seal the deal on coaching changes and purposely threw a game in a dramatic way. If you're going to throw one, what team is going to take advantage of the openings you give them and run up the score more than the Patriots? And easy to drop passes and fumble with all that snow around. Oops. It slipped.
Personally, to lose as historically as they did yesterday, I think the second is more likely. Although it requires a conspiracy theory to believe it, I'd almost rather believe that they did it on purpose.
In any case, either scenario, doesn't matter, I'm pretty certain that this is Coach Fisher's last year here, for better or worse.