Higher prices on corn kills China.
[Corn] in the killbox is really [corn is a problem for who?] Which is [China].
When you have a country bursting at the seams with people, what do you need to keep that country stable? A lot of things, but the most important is jobs, water, and food.
If you're in a trade war with a country like that, and you can apply minor pressure to your people (lower quality fuel) in order to apply MASSIVE pressure to your enemy (higher prices on food = angry civilians going on long walks)…it's a major weapon.
Add to that tariffs that limit the countries access to the market of last resort (the US) and you now have businesses that are struggling to stay afloat. I work in an industry requiring corn and, often, Chinese goods. We've already switched to European sources because availability is sparse, reliability and quality have all degraded, and cost has gone up. A day does not go by that I do not get contacted by at least 2 new Chinese firms peddling garbage rip off goods all in broken English. It's gotten worst since Trump. They're getting desperate.
So corn is a major move against an imposing foe who is trying to assert themselves on the world stage. Looking at it from that lens…