Most of the voters in the polls go on name recognition and reputation. To their credit, though, Boise played no 1AA schools and had six bowl eligible teams on their schedule: the other four in their conference plus BYU and MSU. Kent had only four bowl eligible teams (BSU, Rutgers, BG and Ohio) and had a 1AA school. NIU had three bowl eligible teams (BSU, CMU, Toledo) and a 1AA school.
Boise's credentials are all well and good, but that doesn't explain how they suddenly jump 7 spots without playing, leapfrogging teams that did play - and won.
Know what DOES explain it? ESPN didn't pay a kajillion dollars to broadcast Kent State in a major bowl game. At least with Boise, they would have a brand-name "little guy."