College stadiums are probably a better target since many are in smaller towns. A stadium in a town with a tiny police force is an easier target than one in Chicago or New York where they have specialized anti-terror police units.
However, I'm betting that this was a work accident and the "victim" was an eco-terrorist on his way to plant the bomb in a bio-science building. He was probably betting that the campus cops would be so focused on the game that he could slip into any building on campus without detection. Unfortunately for him, the bomb was unstable.
If you presume the bomber was foreign national of Islamic religion and I do, then a college town with lots of foreign nationals provides an opportunity to blend into a crowd without notice. Individuals with such a background would have a difficult time going relatively unnoticed at an NFL game, particularly say a Packer home game.