It's the trademark that matters i thought (possibly naively), since anthropic.ai was registered in 2020 for a product built in 2019, it seems, and the Anthropic spin off from OpenAI was formed in 2021, seems to have purchased a squatted domain name of anthropic.com then.
Well you can also buy a trademark, right? Though I think different companies are allowed the same trademarks if the things being trademarked aren’t confusable
Kind of unsure how it all works.