In the past, farmers protected themselves by diversifying. The corn croppers feed out cattle/hogs, plants beans or some other grain. That’s harder to do now with the huge mega-acreage corn growers. The easiest transition is to beans.
Hasn’t been that way for a long time, though it has gotten worse in the last 20 years.
My grandpa planted oats and wheat on one field, while having a rotation of alfalfa to “enrich” the soil (good nitrogen fixer).
Some farmers do that. Now the focus is on corn, using fertilizer to regenerate the soil. Some still use corn/beans/alfalfa rotation, but they are in the minority.