The fact is: mobile software as a market has plateaued and everyone in the ecosystem is looking around and seeing lots of profits being made by the 2 world largest digital brokers: apple and google, and very little options. It just makes economical sense to become letigious and look for other allies against the State of affairs.
I'm sure Epic also took into consideration that any blocking of their app on the store will have little inmediate impact on their bottom line (since they are already very popular and already installed by most who would want to install).
Those who already have the update can already start sending epic money without paying "apple tax".
Sure, epic won't be able to release updates until this situation is resolved but I don't think this has much short term impact on their business for reason states above.
Apple could resort to erasing apps from people's device but that would only help Epic (and EU, and Spotify and all those who are shouting "Monopoly" at Apple).