Google would lose if they would continue hammering the interop point and the justices would dig deeper. Google only copied a selective set of Oracle's Java libraries. If they were about interop, they would have copied all of them. So no, Google didn't copy the libraries because of interoperability reasons. Google copied them so they would get access to the large developer community and ride the coattails of the successful investments into the Java platform that Oracle made. As one of the justices said, it's a one-way interoperability.

> Google copied them so they would get access to the large developer community and ride the coattails of the successful investments into the Java platform that Oracle made.

I like this framing and think it’s entirely correct, but I don’t agree that it necessarily dooms the interoperability argument.

Google wasn’t trying to achieve compatibility with existing code (for which, you’re right, they’d have needed to take the whole set) but rather compatibility with existing developers. Arguably, that is still interoperability.

I see your point. But because it would be interoperable with the developers and not the end users, so it’s still no dice for Google. The QWERTY keyboard is a good example of interoperability with end users (but not of copyright itself). So the courts would not give weight to that aspect.