Because people think the progress shown with gpt5 is unimpressive. Meanwhile Claude is very successful, Grok has come out of nowhere and according to some benchmarks matches or exceeds gpt5 slightly. Meaning openai might not be THE horse to bet on. Doesn’t mean there isn’t a race going on with the potential for a big prize at the end, even at current valuations. Only time will tell! As per usual!

But that's just ... Not what a bubble is. A market leader having viable competitors doesn't make them any less of a market leader, and doesn't make them "a bubble".