I have a strong suspicion that previous generations of TPU were not cost effective for decent AI, explaining Google's reluctance to release complex models. They have had superior translation for years, for example. But scaling it up to the world population? Not possible with TPUs.

It was OpenAI that showed you can actually deploy a large model, like GPT-4, to a large audience. Maybe Google didn't reach the cost efficiency with just internal use that NVIDIA does.