Search engines wouldn't work without the fair use doctrine, period. Otherwise a google search would be something like hundreds of thousands of dollars of copyright violations per search.

OpenAI doesn't seem to do anything different than Google. They can own a private library of copyrighted works and index/model it how ever they choose. They can offer products on that index/model in creative ways. And AFAICT, they don't distribute the index/model nor the raw training set to others.

Now artists may not like it, and we as a society may not like it, but it looks like they're not doing anything illegal. And to be fair, a court would have to slice the baby super thin here to allow Google to do their indexing, but not OpenAI.