Make them a ruthless and ever-expanding megacorporation.
If you make your plum corporation into a massive and ruthless monopoly, then the problems will multiply exponentially.
You already mention that they produce more plums than the entirety of the country's production. This means they not only have the entirety of the home nation's plum supply under their control, but they also have the supplies of other plum companies under their thumb too. Anyone who wants to buy plums has to go through them first. Being a monopoly means they pretty much get to set the price too, so the cost of plums will probably skyrocket.
Since these people sound pretty cutthroat and there are even other species such as angels and demons in this world, then maybe this plum corporation has the help of some genuinely powerful beings and is thus capable of overthrowing anybody who gets in the way. The corporation spreads like a virus and soon they have the plum supply of the whole world in the palm of their hands.
Now that they have the whole supply, they need to find a way to keep their profits rolling and people buying at super high prices, so they use their newfound funds to run a massive ad campaign.
News corporations start pumping out pieces talking about the health benefits of plums, eventually dissolving into outright lies. It goes from "eating plums will make you healthy" to "eating plums will make you immortal!". This product is the cure for everything. It'll make you faster, smarter, and more attractive. There is nothing they cannot do, so buy more now!
Once they have the media conquered, the corporation still needs more money, so they resort to even more drastic measures. They start making tons of new plum-based products, starting with basic stuff like plum juice or maybe plum-flavored fruit snacks, and then they go to more ridiculous stuff like plum-flavored pizza or plum-flavored meatloaf. Soon every product known to man can now be made of or have the flavor of plums.
As their profits mount, the company does everything they can to put products everywhere. Every commercial will spout this corporation's praises. Every major actor will endorse them.
Product placement on every billboard, every wall, and every square centimeter of space.
There really is no end to how insane you could make this.
Every piece of clothing has the company logo on it. Classes such as history and math are now replaced with how to tend to plums. As soon as the kids leave school, they get sent to the factory to make money, and then told to spend all that money back on buying company products.
Politicians have all been bought out, so now even they are endorsers of the company. Forget policies and governing. We need to talk about how amazing the plum company is, and how we can ramp up plum production.
If you really want to go off the deep end, make it an outright cult. People worship the company now. Plums are sacred fruit. Every major world religion is replaced with the Church of the Plum. They could have a holy book and everything.
People no longer say "Good Morning". They say "Have a plum day!"
People paint themselves purple to embrace their fruity nature.
Names like Josh and Bob are gone now. The most common name is just Plum. The leader of the corporation is simply called the Great Plum. All shall worship the Great Plum or despair.
It's over the top and super ridiculous, but I feel like this is exactly the kind of thing I think a fun video game could need to make it memorable. Honestly, I could keep coming up with plum-related ideas all day.