I think this concern is not really reasonable given that there are a vast array of LLMs, now including completely open weight frontier tier models. The valuations of certain companies is nothing but a bubble. What logic exists for it is probably in one part praying for a government granted monopoly, and in part relying on the LLM companies being deemed too big to fail when the bubble bursts. The latter part is also probably true, and a yet another good reason that too big to fail is the dumbest logic ever - rather than protecting the economy, it directly drives self destructive behavior.