I think one of the reasons Apple feels entitled to do this is almost monopolistic US market share. People should stop buying iPhones for this, but it's not hard to foreseen it won't happen.
Apple has a far from monopolistic US market share for mobile devices. They might be one of the largest single vendors, but if I want to go buy a new smartphone that has decent app and service support from the marketplace, I can absolutely do that without giving so much as a penny to Apple.
I don't think this simplistic view of "monopoly" is all that useful today. This article, IMO, is proof of that: Apple is forcing an unrelated company to change something fundamental about how they take payments, which (negatively!) affects that company's customers (both patrons and creators), even those who do not use Apple products at all.
If that's not abuse of market power, I'm not sure what is, then.
Apple has just over 60% of the US market share and employee a whole arsenal of tactics to create artificial friction with other platforms in order to increase that market share.
That's big, but in the minds of most, that's not a monopoly. Duopoly with Google, sure, but convincing a court of a monopoly when a lot of people in that court have living memory of Windows being 80%+ of the total OS installs in the country is going to be a tall ask, especially considering that didn't even stick, long-term, as a rationale to keep MS under the original terms of its punishment.
