ChatGPT isn't a multi trillion dollar product though, what they mean is that AI products doesn't today work well enough to warrant trillions of dollars in market cap that you see in NVIDIA etc.
It comes down to how many of these offerings can deliver value worth $X/month to fund the multi-billion dollar ventures behind them, where companies find that they are willing to pay that $X per seat for it.
There must be at least 6 major players among OpenAI, Microsoft, Google, Meta, Apple, Stability, and more that I haven't kept track of. NVIDIA has no way of knowing how viable all these businesses are in the medium term, they know how many GPUs they're buying while investment capital is flowing to them.
You are correct chatgpt is a great product. But if thats the only 'AI' product, or there is a handful. Those companies will focus on replacing NVIDIA ASAP. NVIDIA benefits from having a broad set of customers.