Being a monopoly is NOT illegal. It seems many people think once a company has a monopoly, they need to be broken into separate pieces. This is fiction. A monopoly would only be illegal if a business uses its monopoly power to stifle competition.
Mere exclusive purchase would be a problem if Apple is defined as a monopoly, and you are forced to use Apple as your vendor to release on iOS.
Also in the EU, having a monopoly is not illegal (as long as it was obtained fairly) - abuse of monopoly power is.
Surely being a monopolist means you are subject to additional rules, no doubt about that.