Other fans watched the Saints games this year because their favorite team was playing them. This stat can't/doesn't decipher if the 15 million was just primarily Saints fans.
These ratings mean almost nothing and are mostly just a product of who you played and when, along with how many national TV games you had going into the year, and market size.
All skewed data.
The Bears are awful every year, but are in a big market and are always playing in primetime, hence why they’re top 10. As of late, the Giants too, for that matter.