Because ranking and seeding are not the same thing. Ranking is done by voters. Seeding is done by a committee. The AP likes wins. UNI is ranked higher, and deserves to be ranked higher, because they have the wins. They have 15 straight victories. They are a hot team.
ISU deserves to be seeded higher. They have a better SOS and RPI. They have more top 50 wins.
Of UNI's fifteen straight wins:
1 has been ranked (at home)
only 5 have been in the top 150 rpi
2 of those five have been on the road