Or MAYBEEEE....Iowa is just not as conservative as you think it is. It has only voted Republican one time since 1988, when Bush barely won it in '04. The state supreme court legalized gay marriage there before a lot of other blue states and the judge who pushed it through was retained by the voters.
Also, Iowa isn't as rural as you think, either. People are increasingly moving to the larger cities there like Des Moines and Cedar Rapids, and the state is becoming more diverse.
This. Isn't Iowa largely a collection of small-ish cities situated on the river?