Iowa uses about 45.7TWh of electricity. Even if all those bars are added together (not including deprecated or replaced systems), we're looking at 480MW of installs - or 0.01% of solar generation in the state. Annual average growth in demand since 1968 has been about 1.47%.
If solar penciled out, they'd be installing it at more than 10% of annual demand increases. If I had to guess, if I keep digging, I'm going to find out Iowa is installing solar for the same reason so many EVs are only available in CA: compliance.