Apple wouldn't have to if they didn't artificially prevent competitor app stores from being installed on iPhones. An app store is just software that tells the OS to install another piece of software. They are not complicated or hard to code, Apple just installs one with your phone and prevents any apps from being installed except through it, and then they refuse to host other app stores.
This is them using their market share in phones, to avoid competing fairly with third party software app stores like Steam.
They claim they have to install every thing through their app store for security reasons and there's no possible other way to build it (horseshit), so rightfully then, to prevent them from illegally tieing two unrelated products together, they have to host Fortnite on the App Store since it has to be the neutral competition hosting level of abstraction. It wouldn't if Apple would allow competitor app stores like they do on MacOS but they won't this is the bed they made.
And let me be frank. Your assertion that Epic is not a good company and Apple is not a good company, in the same breadth, is false equivalency horseshit.
Apple charges mafia 30% of all software REVENUE fees in addition to their other anti-competitive bullshit. They use their dominant platform position to be an absolute drag on the economy at large. Epic bought some game exclusives for a couple years. They are not comparable.
Please do us all a favour and go and read the Wikipedia article on anti-competitive behaviour and anti-competition laws before commenting.
And just in case you lack the mental faculties to actually parse that Wikipedia article, the key lesson we're looking for you to learn is that you do not need a a monopoly to behave anti-competitively, you just need market power, and to abuse it in a way that avoids fairly competing on the merits of your product.
Apple forcing people to use their payment system for no reason other than it lets them make more money, is anti-competitive behaviour. They are not competing on the merits of the best payment system, they are using their dominant market share in phones to force people to use their payment system where they can charge whatever they want.
Quite frankly, there are a huge number of examples in society of companies behaving anti-competitively. It's largely what happens when you let business people run things, since they can organize your company structure and reporting to be efficient, and then they run out of ideas for legitimate ways to improve the company's products.
Anti-competitive tying is a long standing, textbook, example of anti-competitive behaviour, it's just often not prevented in the US because US law basically requires you to have a full monopoly before anyone will do anything which is dumb as tits. It'd be like in hockey if the refs were only able to give you a penalty after all your opponents were too injured to play anymore.
It also ignores other ways of gaining and abusing market power. Walmart is the textbook example of a monopsony, where there market power comes not from being the only store, but the only customer, they are famous for using their size to crush and control their suppliers in ways that are flat out illegal in most of the western world.
At the end of the day, our economic system is based on the idea that people should compete to produce the best product or service, and then consumers will reward the best one with proportionally more resources based on which one is their preference (best, cheapest, etc.). That falls apart when you start using software to artificially tie every product to every other product. Suddenly AI can't fairly compete to produce the speaker without also producing a phone, and watch, and laptop, and have everyone have a network of friends and family all also using those. It literally undermines the entirety of capitalism.