My conspiracy theory is at healthier foods are deliberately made more expensive, to push people into the cheaper ultra processed foods. It's kind of like cigarettes, push them into the more addictive, cheaper products to hook them.
Its more a matter of whats subsidized. All that corn grown thanks to the corn and soy bills passed to support midwestern farmers are used for things such as plumping up cows/pigs/etc, used for a inefficient form of fuel (biodiesel, E85), and finally pumped into all the foods as HFCS among other things. The farmers can keep growing unproductive crops and stay in business (so politicians won't be hearing from them), the government can ensure the farmland processes will be available during wartime and they can check off their requirements of ensuring all citizens have a minimal required number of "calories".
Its a symptom of same thing that is messing up the US in all other areas. Poor governance caused by layers of people all along the stack taking their cut and not caring about the overall picture.
No need to invoke conspiracies here when the ultraprocessing makes food last longer, more delicious, and allows manufacturers to skimp on more expensive ingredients (eg. "ice cream" that use thickeners rather than actual cream).
