It’s important in the fair use assessment to understand that the training itself is fair use, but the pirating of the books is the issue at hand here, and is what Anthropic “whoopsied” into in acquiring the training data.
Buying used copies of books, scanning them, and training on it is fine.
Rainbows End was prescient in many ways.
It’s crazy to imagine, but there was surely a document or slack message thread discussing where to get thousands of books, and they just decided to pirate them and that was OK. This was entirely a decision based on ease or cost, not based on the assumption it was legal. Piracy can result in jail time IIRC, so honestly it’s lucky the employee who suggested this, or took the action avoided direct legal liability.
Oh and I’m pretty sure other companies (meta) are in litigation over this issue, and the publishers knew that settlement below the full legal limit would limit future revenue.