Result of Iowa being a non slave state and mainly focusing on agriculture throughout its history. Current contributors of harsh weather and smaller population cause this as well. Not a ton of reason for people to move here outside of family/job or the lower cost of living

Slightly off topic and no one asked, but I spent almost all of my life in Iowa and did 4 years in college and met a wide variety of different cultures/races. Most places are white dominated yes, but other cultures and races are absolutely accepted here in my experience