I like to compare it to Carroll football. Back when Carroll was dominating and going through 4-straight titles, they were providing great football on the field. But after having attended my first Griz game in 2007, I could never look at Carroll the same again. The atmosphere wasn't even close to that of a Griz game, and even watching Carroll games on TV were boring, because there was no atmosphere. And Carroll football atmosphere is comparable to a lot of FCS programs.
The same goes for the average FBS fan... they want to watch games that are played in packed houses and have raucous atmospheres like what many are accustomed to. It doesn't matter if there is good football being played on the field if there isn't a full crowd and great atmosphere to go along with it. Fans may watch a little bit of the game but eventually they'll move on and do something else if it doesn't keep them hooked. ESPN wanted NDSU/Montana in 2014 because they knew it would sell to football fans. EWU was lucky they ended up getting it when both NDSU and Montana said "no". And if you don't think the atmosphere of a game drives the decisions for sports television, then you have to question why ROOT Sports has said numerous times that they love coming to Missoula to air games. Bottom line is that the atmosphere is a big deciding factor for who ESPN chooses to air on TV because they know that's what will help draw in viewers.