Microsoft hit all time highs just on the possibility that they hire Altman. It almost certainly didn’t go even higher because it’s still not a sure thing. If it actually happens I think the market will value Microsoft even higher.
Wrt whether it’s just the market itself or openai, note that news of sama’s firing caused ms shares a steep drop. Then news of sama’s employment with msft help set the share price at least back to where it was before.