When Google did that, Google was relying on controlling precedents in the 9th circuit saying that APIs are functional elements needed for interoperability and therefore are not copyrightable. The first judge that they saw agreed with them and it should have been an open and shut case.

It was Google's misfortune that through a quirk of the system the case wound up in the Federal Circuit, which has a history of creatively ignoring precedent to fashion new precedent that increases its own importance. (Which is how we have patents on all sorts of crap that the Supreme Court has ruled that we shouldn't.) And it was good lawyering on Oracle's part to throw every possible argument at the case, including the copyright arguments that they knew they should have lost.