They breached their contract with Apple, then filed a lawsuit against Apple and launched an anti-Apple marketing campaign. Apple has every reason to cease doing business with them.
They have a valid point in their lawsuit regarding in-app payment methods. Apple forces apps to use their in-app payment solution for digital goods that can be consumed in-app (movies, music, game stuff etc), yet amazon is the odd one out with special treatment allowing them to for one get only 15% taken off and also use their own payment processing with rentals and purchases in the Prime app.
The whole „everyone gets treated fairly“ is hyperbolic as fuck coming from Apple.
Just look up the origin of their „Reader app“ clause, it‘s a gigantic special treatment factory so apps like Netflix and co. didn‘t just kill their apps day 1, leaving Apple TV and co. dead in the water.
Apple bends their own rulesets where they see fit, it‘s not a fair ecosystem at all yet everyone goes at Epic for being the odd one out there, actually trying to fight for fair treatment between all apps.
Disclaimer: I hate Epic for their Epic Store exclusivity practice, but I agree with them that Apple is borderline retarded when it comes to developer relations and treatment. Xcloud being another mind boggling and ancient way of thinking just to cover their backs (e.g. streaming killing native apps one day, rendering the App Store obsolete).