I don't think Microsoft is audacious or competent enough to orchestrate a fictitious termination, that's a little too far fetched. The initial event _reeks_ of incompetence/AGI fear-mongering, not orchestration.
+24 hours - Nadella announcing the creation of an internal OpenAI and automatic employment offers to all OpenAI employees. Seems sensible. Microsoft's investment in OpenAI entitles them to 75% of all of OpenAI's net profit until they make their whole $13B investment back, not to mention retain ownership of 49% of OpenAI. Too much capital to play chess with, the division/auto-hire announcement still feels like it must have been done with a lot of hesitation and picking the least awful option, but what else? If the conclusion is that OpenAI's board is prepared to sabotage the company -- and the exceptionally vague (=> bullshit) reasoning OpenAI published for his termination supports that conclusion -- there's no other option.
But +48-72 hours, this is perhaps when the "holy shit" moment happened -- Bing's lifelong irrelevance as a consumer product and sudden ascension to relevance as Google's defense in an extremely serious lawsuit, and at least Google organically beat the other search engines.
The Microsoft board realized hemorrhaging OpenAI, whilst also probably owning xx% of all H100's (arguably the defining competitive advantage of GPT-as-a-Service co's), would almost definitely lead to them being in Google's predicament years down the line. By then, the FTC will not care that the "trigger" all those years ago was a board that became frantic about AGI, with Microsoft merely rescuing a ship that self-sabotaged.
So the chess started here, Ctrl+Z'ing everything, the overtly outward displays of compassion, some genuine, some perhaps encouraged, and everyone - including Sam - is back on the same page that Microsoft needs to back off, but crucially it has to appear as a reunification stemming from within OpenAI.
It is precisely at this point, in this chain of events, that the opportunity emerges for a OpenAI board replacement, with Sam being firmly on it, that is in line with Microsofts deep (arguably trauma-laden) desire to finally be the dominant player in something other than desktop operating systems.
No source, I doubt there will ever be, but this speculation of events, to me, lines up most with the actions of the parties involved.