By virtue of winning the conference and regular-season title, Michigan, North Dakota and Boston University received automatic byes. The coaches voted to implement this rule a couple of years ago. The final bye went to Clarkson, which clearly beat out the remaining teams in the East. The committee won't give a team which is geographically outside a region a bye unless there is an overwhelmingly compelling reason do so, and in this case, there wasn't. Now, however, you have uneven regions, because seven Western teams qualified.
Policy then dictates that two non-bye teams from each region be switched to the other.
The committee first attempts to take the bottom two from each region, but if that would negatively impact attendance in a severe way, or create intra-conference matchups, different teams can be moved. This occurred last year, when Mass-Lowell was moved West. In this case, moving the bottom two worked out perfectly, especially since doing so sent Michigan State back West, where the committee was going to ensure it was anyway. There was some debate in the East, however. Some members of the committee thought it was a no-brainer to keep Vermont and New Hampshire in the East, no matter the numbers, because of their huge draws.