The MAC certainly hurt themselves this year by having an extremely competitive conference where the teams beat up on each other quite often. Personally, I'd rather see Bowling Green, Buffalo, or Ohio in the tournament than a team like Notre Dame or Mississippi State. The issue is that the numbers don't look to be in the favour of the MAC with a best NET ranking of 56 held by Bowling Green. So, the computers not helping their case with the lack of respect the MAC gets as a conference probably means that they're a one bid conference this year despite multiple recent deep runs in the tournament by CMU and Buffalo.
It was more than an issue of the better teams in the MAC beating up on each other. They also lost too many games to the middle and bottom of the conference. Ohio is a good example, since in theory they entered conference play in the best position to build an at-large-worthy resume with the win over Notre Dame (with ND missing two key players, but still).
But Ohio's losses came not only to the top 3 other teams in the conference (Bowling Green, Central Michigan, Buffalo). They also lost to Eastern Michigan, Ball State, Kent State and Akron. Just not a good overall resume.
I don't like reading too much into one game, but I find eye-opening the fact that the team that won the regular season title by 1.5 games (Bowling Green) lost to a pretty lame Purdue team this year.