How long have they been back on campus? If its just been in June they had it before this started up. Frankly younger people aren't following isolation guideline(see Memorial Day). Student athletes are not different and many are likely taking risks that will lead to exposure and infection.There are dots being connected that don't necessarily connect.
It's entirely possible that the staff member and the student-athletes are separate instances, and not that they all got it as a result of being at the facilities.