This was bound to happen. I guess Epic's goal was just to stir some shit.
A lot of current law around things like app stores is existing in the liminal space of "Are these restrictions legal? Nobody knows. Do you want to be the one who stakes all your company's money and your investors' money and your entire business model on finding out?"
Epic did the calculus and seemed to conclude they wanted to be the ones to take the hit (possibly because since they also own their own app store, the math was a little win-win: any lock-in the courts find Apple has applies to the way Epic runs their store also). It hasn't worked out the way they'd hoped (though the anti-steering decision was interesting and a little surprising).
I think the most generous interpretation of this lawsuit is that it's a publicity stunt from Epic, not for consumers, but to pressure legislators.
Perhaps not a likely scenario, but US law is highly path-dependent and at the end of the day, judges' interpretations of law and precedent are all that matters regarding the correctness of a court decision.
If they had just sued without changing the iOS app to allow in-app purchases without using Apple's IAP, then Apple would likely have been punished if they still suspended Epic's account.