Not sure how Alabama works, at WVU the athletic department pays tuition for the athletes on scholarship. The money generated from the athletic programs stays in the athletic department.
According to what I read in a few articles, the athletic departments spend money from revenue on athletic things that the university would normally be required to cover. Probably the biggest assets are stadiums and play toys like computerized screens for their athletic fields that are considered real property and would be the responsibility of the university. thus freeing up funds for other departments and their needs. The colleges in the case of the big earners like Bama, Notre Dame, and Tennessee run a loan program to the university to supplement the other university programs while covering other sports needs for the college and building their worth.
So, as the money goes out, it is used to replace the need at the college so they can spend it for academics or borrow it.
rwood