I follow them. rumor is their RPI was not that strong. but I think it is a snub. they've made it to the sweet 16 in 2013 and 2012, and hovered around 10th in the rankings most of the year. probably a P5 thing versus a G5 thing.
not being seeded I think gave them a chip on their should and a "us against the world" type of attitude, which can serve a team well.