Has nothing to do with a QB. They had Scott Tolzien the last couple years and their fans were just as engaged.
Madison is easily as good a college football environment I have ever seen (Notre Dame, Tennessee, Penn State, Florida, USC included) and their fans are rabid. Games are attended by generations of families who attended Wisconsin and they have stayed loyal through some pretty rough years. A large part of the charm of Camp Randall is its' proximity to the rest of campus, with bars, tailgating, dorms and restaurants all within a walkable distance. Not sure how we'd ever get close to that in East Hartford.
As an aside, seeing the student section jump up and down at the end of the 3rd quarter when House of Pain's "Jump Around" plays is a sight to be seen.