I think the expectation is that as companies begin drawing moats around their data, it will be harder for new players to enter the market. As these models progress, it will just get more expensive to compete, so only the big players will have a shot. OpenAI might only have a slight advantage at the moment, but they have proven they can do it, they have the talent necessary to continue to innovate, and some great backers, including the government through Larry Summers. All they need is a boatload of money, and that's exactly what they are getting through their huge valuation.

I have no idea if that reasoning is sound, but it is at least plausible. I've compared most of the big LLMs, and OpenAI still has a really solid lead imo., mostly due to tooling. But I also suspect they are very close to GPT5, but will wait to release it until they have serious competition, eg. through Gemini.