Perhaps more urban areas, perhaps (in 2012 anyway) Iowa's economy is good, giving it a favorable view of Obama. Maybe it's just closer to Minnesota than Kansas and Nebraska
It's not about Obama, it has been leaning Democrat long before him. Iowa has similar sized cities to Kansas and Nebraska, Minnesota has a very large urban area which helps Democrats. Minnesota and Wisconsin are more similar, Iowa is just a state I don't understand. Every other state I understand why it votes the way it does even Colorado, but not Iowa.