About half of Missouri's electrical power comes from coal. The national trend is utilities ramping up on solar, wind and battery storage while relying less on coal, causing some coal plants to shut down. I wouldn't be surprised if this legislation to stop new solar is being pushed by the coal industry.
It's sad that the party of small government has absolutely no problem telling companies and people what they can and can't do on their land, etc. So, as expected, it's ok to do or say what they want, just not what you want.