Close. WWII America had to invest heavily in farms to feed soldiers who need 4,000 kcal diets to support marching around with heavy packs all day long in potentially cold weather. That investment drove up automation in the farm industry, particularly with corn and soybeans.

War ends, but the infrastructure is all still there. If farms weren't heavily subsidized, they would collapse. There was real risk of fields going fallow on a mass level, resulting in too little food to feed the population. And then you have to keep subsidizing it, forever. Nobody has figured out a way out of that logic while maintaining a mostly capitalist production system.