As part of selling on Apple's app store, you agree to follow the ToS. The ToS are very clear that you don't set up your own marketplace inside your app where Apple doesn't get a cut. This reaction (terminating Epic's account) was eminently foreseeable and completely justified. You do not fuck with Apple's cut. Don't like it, don't sell on the app store.

Epic thought they were big enough and valuable enough that they could bully their way through ToS violations. All the hip thinkpieces were saying that no matter what happens here Epic comes out on top, because Apple has everything to lose and blah blah.

Turns out nope, Epic's customers do need the app store after all, so Apple has the leverage here after all.