You can't really compare market caps like that. Addressable market or market share is only one piece of the puzzle, and the other companies you mention are in very different kinds of markets, with very different kinds of products, with very different kinds of costs and margins.

A valuation just reflects what someone thinks about the future cash flows of the business.

But yeah, it does feel a bit crazy; unsurprisingly, AI hype affects valuations of AI companies too. On the other hand, I can see the idea that some people might be betting on the idea that the big US labs are bloated and spend too much money, and that the real money is going to be in serving open-weight models, and/or in automatically combining and routing to different models based on the task at hand.