I don't know, for all their successes (like Unreal Engine) they been burning a lot of cash trying to capture market share from Steam with only limited success. At some point something gotta break
Epic does not rake in the big bucks from Unreal Engine. They waive Unreal Engine royalties on games that use it until revenue reaches $1 million. If the games are published on the Epic Game Store, they won't collect even if those games are big sellers.
Again, Epic takes a percentage of game sales on the Epic Game Store. This was heavily covered during their litigation with Apple. They aren't giving games away from free. They are also a publisher and thus take a cut of sales from those titles.
Their big play is for GaaS, which in practice translates to ongoing subscriptions, in-game purchases, microtransactions, etc. Fortnite is free to play, they make their money from cosmetics, etc.
My guess is that the PC video game universe can support multiple storefronts. Note that Epic Games has a mobile presence on Android. They had an EGS app on iOS but following their unsuccessful litigation with Apple, the end result is that they got kicked out of the iOS/iPadOS market.
Amusingly, Apple users can still play Fortnite via GeForce NOW both on iDevices as well as Mac.
One of the major factors that has driven Unreal Engine success is its portability: desktop, console, mobile, and VR.
