Meta is a company though, not (primarily) a brand. People don't need to google or remember "Meta"; they'll search for "WhatsApp", "Instagram" etc. (In fact, I suspect that getting as far away in semantic space from Facebook with these other properties was part of the motivation for the rename.)

If OpenAI renamed itself to just "AI" I'd sigh and shrug (and applaud the honesty), but ChatGPT is a product and well-known brand name.