Fortnight coming to iOS was a big deal for Apple. From what I've read or watched (though I can't site any sources now), Apple worked closely with Epic to get it running well on iOS. I was developing a game for UE4 at the time, and had seen optimisations that were done to the game that were later released as new features in the engine, which we could then use on our own games on all platforms.
And now for some speculation.
At this point, I believe that Apple was thinking about a further partnership with Epic. After all, the biggest game on the planet and the hottest game engine in the industry were now running on all Apple platforms and Apple was aware internally that the M1 was on its way - which would mean that the whole Apple ecosystem would now be viable for gaming. Whether this partnership was simply placing Apple engineers on site to ensure that MacOS and iOS would remain in the forefront or UE4 and UE5 development, or publishing / licensing deals, who knows.
Then of course, we know what happened and that partnership is no more. Since then, support for iOS in UE4 hasn't been great. There have been some bugs such as some basic Augmented Reality features being unimplemented for years, and Intellisense / Code-complete on XCode has been broken for a while too (so it makes more sense to develop purely on a Windows PC, and only use a Mac for making iOS builds).
I believe that Apple learned a couple of lessons from this:
1. Having a wildly popular game on your platform can generate significant income (who knew???)
2. If you support a AAA studio or engine developer, such games can thrive on your platforms.
3. This all happened by chance because Apple was adopting a "build it and they will come approach". Maybe they approached Epic or vice-versa regarding the iOS port, but Fortnite on iOS mostly happened because of the platform's market share, and the generally good CPU and GPU performance on iPhones and iPads. Because of how organically it came to being, it's not surprising that it organically stopped being a thing too.
4. Apple had no control over any of this. Apple isn't used to not being in control. Being a mere gatekeeper isn't enough anymore, because developers can just opt to not release content on your platform (just ask Netflix what it's like not having any Disney content any more).
5. Just because iOS has a strong market share of mobile gaming now, it's not infallible.
So, how does EA fit into this?
Since the games industry is still pretty lucrative, and the build-it-and-they-will-come approach leaves potential income completely to chance, it makes sense to absorb one of the bigger game publishers and developers in the world to guarantee and expand on the library of games that appear on iOS (thus encouraging people to stick to the platform) and expand that to MacOS.
Apple will also gain control of the Frostbite engine (and other engines) used internally by EA and may opt to develop it into a publicly available Unreal Engine rival, with licensing that encourages developers to release their games on iOS and MacOS. Effectively, they'll be doing what Epic is already doing and attempting to take market share from them.
This will obviously require a lot of work by everyone involved to turn into a reality, and it's not a given that this will profit Apple in 5 years time. It all depends on whether Apple thinks it's leaving money on the table.