It's self evident that apple was engaging in anticompetitive behavior first, because you yourself said they've been operating unchanged for ~15 years, and they're getting in trouble for it now. The obvious conclusion to draw here is that their behavior was always bad.

Indeed, your entire argument relies on some rule about anticompetitive behavior apparently invented just now, something to do with market size? Maybe if we were talking about monopolies, that would be relevant. But a business of 1 user can engage in anticompetitive behavior by locking the user into their ecosystem, or restricting what they can do with their property when it involves competitors.

Apple should have made better choices, earlier: They're engaging in anticompetitive behavior now, so if you claim that they're unchanged, that means they were engaging in anticompetitive behavior before, too. Your framing and claims to the contrary, then, we see are patently ridiculous.