The main problem is how they accessed the IP, but then using it to train a model is fair use. But yeah, IP theft doesn't exist because nothing is stolen really: Hollywood studios still have their movies.
Disney is not just selling tickets to movies to make their money. They are selling licenses that provide the rights to watch, store, and use those movies (or aspects of them) in certain ways. One thing that that Anthropic didn't do is pay the publishers and authors for the right to train their models on the intellectual property. And that's why they have no place pointing fingers at Alibaba saying that they stole their IP.