School dont have to be directly in said city.. just close enough. I get your point, but if that was true, why do superstars flood to big markets in free agency in NBA?
Short answer, those big markets have big market professional teams. They are consider big market because of the size of the population.
In comparison "big market" in college would likely be these schools (based on fans in seats).
Michigan, Penn State, A&M,
Tennessee, LSU,
Ohio State, Alabama, Texas, Georgia, Florida, Auburn, Oklahoma, Nebraska, Clemson, Notre Dame, Wisconsin
Bold names have some of the largest basketball arenas as well.
So UT has the 4th largest football stadium and the 5th largest basketball arena in the NCAA...we're actually the best "big market" for college sports!!!