The Sun Belt has bigger names than the MAC; they probably don't have to play on Tuesdays to get a decent enough deal. While attendance itself isn't the perfect metric (and MAC attendance is hurt by the midweek stuff), the MAC had five teams (Buffalo, CMU, Ohio, Toledo, WMU) that averaged at least 15,000 fans (the latter three averaged 20,000) announced. The Sun Belt had six over 20,000 (App State, GA Southern, JMU, Marshall, Southern Miss, Troy) and one (App State) over 30,000.
Your second point, however, is 100% spot on. The midweek games reduce that access for the fans locally, and that's really the last thing any of the MAC teams need.