Personally I think Microsoft's stock is crashing less about any of this (though it is a hell of a theory IMO) and more to do with the fact that:
* They are investing in AI, both financially and by corporate communication, over and above everything else and pissing off damn near everyone in the process
* The XBox brand is tanking
* Windows is an utter disaster, according to Microsoft themselves, and Valve is so dispirited with it as the future for gaming that they've invested millions into a linux-based framework to run Windows games
Love the last line, what Valve has done on Windows emulation is herculean, I don't know (it would be great to know) other businesses creating/investing in incredible and risky third-party compatible technologies to run their real business on top of it.
I worked in what other calls "Adversarial Interoperability" [1] but the scale of Valve is on another level.
[1] https://www.nektra.com/main/2020/01/12/reflecting-on-16-year...
I’m a little impressed at how a company whose business model is to sell a product they developed in the 1990s over and over again while making inconsequential and non-breaking changes from year to year somehow still manage to screw that up. In my own opinion, they have always been a diabolical company. I’m glad to see them fail.