It's just one example but one of the stated reasons was culture. There's more of it in Chicago.
I happen to be sitting right in the middle of Dallas as I type this, and I do like Dallas. But it's not what I would call a "world class" city culturally, whereas Chicago is. That isn't a small thing.
Population projections for both areas out to 2040 for roughly the same level of growth, by the way.
