Given that Google invented Transformer architecture (and Google AI continues to do foundational R&D on ML architecture) — and that Google's TPUs don't even support the most common ML standards, but require their own training and inference frameworks — I would assume that "the point" of TPUs from Google's perspective, has less to do with running LLMs, and more to do with running weird experimental custom model architectures that don't even exist as journal papers yet.
I would bet money that TPUs are at least better at doing AI research than anything Nvidia will sell you. That alone might be enough for Google to keep getting some new ones fabbed each year. The TPUs you can rent on Google Cloud might very well just be hardware requisitioned by the AI team, for the AI team, that they aren't always using to capacity, and so is "earning out" its CapEx through public rentals.
TPUs are maybe also better at other things Google does internally, too. Running inference on YouTube's audio+video-input timecoded-captions-output model, say.
I would bet money that TPUs are at least better at doing AI research than anything Nvidia will sell you. That alone might be enough for Google to keep getting some new ones fabbed each year. The TPUs you can rent on Google Cloud might very well just be hardware requisitioned by the AI team, for the AI team, that they aren't always using to capacity, and so is "earning out" its CapEx through public rentals.
TPUs are maybe also better at other things Google does internally, too. Running inference on YouTube's audio+video-input timecoded-captions-output model, say.