I think the oomph behind the story is due to it being embarrassing, rather than illegal.
Not illegal, but that won't stop people from finding it amusing that the company considered the world's beacon of innovation is copying someone else's homework. It's hard being the favorite horse.
tech companies steal ideas all the time. snapchat invented stories and now whatsapp, facebook, instagram, tiktok, youtube have them
I don't think google has really been considered a beacon of innovation for a number of years.
OpenAI could have blocked Google's accounts, for example. Nothing really to do with legality.
No one is alleging that Google directly used OpenAI's API to get training data (which would be unambiguously against TOS). The claim is that they downloaded examples from ShareGPT.