Also keep in mind that Microsoft hasn't actually given OpenAI $13 Billion because much of that is in the form of Azure credits.
So this could end up being the cheapest acquisition for Microsoft: They get a $90 Billion company for peanuts.
[1] https://stratechery.com/2023/openais-misalignment-and-micros...
If they let msft "loot" all their IP then they lose any type of leverage they might still have, and if they did it due to some ideological reason I could see why they might prefer to choose a scorched earth policy.
Given that they refused to resign seems like they prefer to fight rather than give it to Sam Altman, which what the msft maneuver looks like defacto.