The US Department of Justice and 16 state and district attorneys general accused Apple of operating an illegal monopoly in the smartphone market in a new antitrust lawsuit. The DOJ and states are accusing Apple of driving up prices for consumers and developers at the expense of making users more reliant on its iPhones.
I think you could analyze it based on a company’s history. Some companies clearly didn’t earn a monopoly, for instance if they had a market handed to them by the government. Or, if they did the thing that’s actually illegal under antitrust law - used a monopoly in one market to expand to another.