Very broadly speaking it's perfectly legal to have a monopoly on something, and Apple has a monopoly on the thing they created, and that's fine. It's generally

Very broadly speaking it's perfectly legal to have a monopoly on something, and Apple has a monopoly on the thing they created, and that's fine. It's generally illegal to use a monopoly on one thing to acquire a monopoly on another thing when that harms society, and that is the claim here. Microsoft alone created windows, that's fine. Microsoft used their monopoly on windows to gain monopolies on other pieces of software, and that was problematic.