Regardless of soil suitability, you can't just shuck off a farm worth (tens of) millions, debt on the same scale (average debt-to-assets as of 2017 is ~13% and I would expect the farmers featured here are way worse) and throw out decades of experience to try and grow mushrooms, it's unlikely that it would make your clients and creditors happy. Even less so when you're in your 50s.
Commodity growers on huge farms distribute their food into large grocers potentially all over the world, to be sold at the lowest possible price. They must maximize yields at any cost to make money. Specialty growers sell into farmer's markets, CSA's, etc, at a much higher cost for the goods. This is why many of them are in coastal and affluent areas, where the buyers are willing to pay considerably more for local, fresh produce that has been grown organically.