Perhaps ChatGPT wasn't the best name for a product and OpenAI would have gone with something more trademarkable if they knew it would become such a hit. Still, my comment above is a simple application of Hanlon's razor.
https://tsdr.uspto.gov/#caseNumber=97733261&caseType=SERIAL_...
(Interestingly enough there's a Chinese ecig/vape company that also looking to trademark ChatGPT.)