In a lot of metro areas that have both a major college and an NFL team, the interest in the NCAA team tends to pale in comparison - e.g. Miami, Atlanta, Chicago. In DFW, TCU has made strides with their recent success. All of those examples are with private schools, however, with somewhat lower enrollment in comparison to the U. Metro areas with comparably sized state flagship schools and an NFL team would be DC (Maryland), Pittsburgh (Pitt), Phoenix (ASU), Oakland (Cal), and Seattle (UW). The one metro area on that list that also has at least as much cultural attraction as the Twin Cities yet manages to support both NCAA and NFL teams is Seattle. Granted, Washington has had more success than the Gophers, but they haven't won their conference in several years (if memory serves). Why can they do it and virtually no one else can?
I do not buy that people in Mankato, St. Cloud, and Duluth refuse to support gopher football because of their hockey programs' rivalry.
Also in regards to Iowa State, Des Moines - a metro of over a half million people - is within about a 40-minute drive or so.