Bishops have a lot of influence on Catholic institutions located within their dioceses, even if they don't have direct control. The last thing a college wants is the local ordinary publicly encouraging parents to boycott their school because it isn't 'Catholic' enough.

The big dogs like Notre Dame and Georgetown can withstand criticism from a bishop, but smaller schools like Benedictine College (not Benedictine University, which is in Illinois) can't. Besides, as you point out, that school skews to the right anyway, so I imagine they have no problem with Naumann's request.