If I had to speculate myself, and this is speculation, Nashville was on the rise when the team came there originally, but the very recent rise (within the last 5-7 years) of Nashville turning into quite the hub for music home studios and/or content creation home studios (that are very professionally owned and operated, mind you) came together more quickly than anyone anticipated, originally.
This incredible buzz led to a lot of notable, well-known talent moving to the city.
This, IMO would be a boon to the local economy, as these companies and individuals are not short on cash by any stretch of the imagination. Combine this with the NFL's desire to have control over the weather for Superbowls, and the NFL has a new, shiny arm of leverage when negotiating Super Bowls with cities that are currently "over-represented" in the usual Superbowl rotation.
You don't have to have much of an imagination to come up with a few cities the NFL might be trying to steer away from, for numerous reasons -- most of which are based on imperfect bias, but I am sure they do also have a couple of good reasons for steering clear of said cities, as well -- if we are truly being objective.