They did not have to, they had an alternate means available (and used it for many of the books), buying physical copies and destructively scanning them.

> and they will not win on their right to commercialize the results of training

That seems an unwarranted conclusion, at best.

> so what good is the Fair Use ruling

If nothing else, assuming the logic of the ruling is followed by the inevitable appeals court decision and becomes binding precedent, it provides a clear road to legally training LLMs on books without copyright issues (combination of "training is fair use" and "destructive scanning for storage and searchability is fair use"), even if the pirating of a subset of the source material in this case were to make Anthropic's existing products prohibited (which I think you are wrong to think is the likely outcome.)