Google had emails saying "guys let's illegally abuse our monopoly to prevent anybody else from competing with us". Apple said "there's one app store period"; no competition possible, no monopoly.

Google got into trouble because they got caught flat footed by iPhone so scrambled to use open-source Linux and free-to-use Java and make money off them. That's why alt app stores are possible for Android and why they had to use patently anticompetitive contracts to lock it down. It's a little bit of karma for knifing Sun in the back.

Hopefully Apple is also forced to have other app stores or sideloading, but it'll be a harder battle in the courts.