... why don't they pay it down with reserve money to avoid paying all that interest has me a little confused.

To be fair, even college football’s dynasties worry about the future. The NCAA is facing legal challenges—specifically, antitrust lawsuits that focus on giving athletes a larger share of sports revenues—that threaten every school. And no one knows how long the media money will keep flowing. “If things stay the way they are,” says Alabama athletic director Bill Battle, “I’m very comfortable.”

Just in case they don’t, Alabama athletics has set aside a reserve fund of about $180 million, enough to cover the costs of the entire athletic department at most top-tier football schools for three years.

https://www.bloomberg.com/news/features/2017-01-09/alabama-trounces-clemson-and-everybody-else-in-the-college-football-money-game