Consider that Satya already landed a huge win by the stock price hitting ATH rather than taking a hit based on the news. Further consider that MS owns 49% of a company which could be valued at 80 billion on the condition that the company makes structural changes to the board to prevent this from happening again (as opposed to taking a dive if the company essentially died.) Then there's the uncertainty of the tech behind Bing's chat (and other AI tie-ins) continuing to be competitive vs Google and other players. If MS had to recreate their own tech, then they would likely be far behind even a stalled OpenAI. Seems to me that it makes little difference where this tech is being developed (in-house vs in a company which you own 49% of) in terms of access. Probably better that the development happens within the company which started all of this and has already been the leader, rather than starting over.