> You have to have a monopoly in a market, of which iPhone is part of the “smartphone” market.

Products and markets are not a one to one mapping. For example, if you sell low-background steel, that's part of the broader "steel" market because anyone who needs ordinary steel could buy it from you and use it for the same purposes as ordinary steel. But low-background steel is also its own market, because the people who need that can't use ordinary steel. Likewise for sellers of products with higher purity levels, products that satisfy particular standards or regulatory requirements, etc. It's only the same market if it's the same thing. Clorox bleach is the same as other bleach; Microsoft Windows is not the same as MacOS.

And iOS is not the same as Android. I mean this really isn't that hard: Are they substitutes for each other? If you have a GE washing machine, can you use any brand of bleach? You can, so they're in the same market. If you have an app that exists for iOS and not Android, can you use an Android device? No, so they're not in the same market. Likewise, if you've written a mobile app and need to distribute it to your customers who have iOS devices, can you use Google Play? Again no, which is what makes them different markets. They're not substitutes, any more than a retailer in Texas is a substitute for a retailer in California when you have customers in both states -- or only have customers in California.