office 365 is the only thing stopping people from switching to linux as the only current alternative is ironically chromeos (android office) and macos (fully supported by microsoft)
I think there is more to it: IT desktop admins mostly trained on the microsoft ecosystem, GPOs, etc.
Compliance checkboxes. That is the true strength of Microsoft - in 365 you are pretty much compliant with everything out of the box or you at least get the tools and reports to achieve compliance, and even the stuff where compliance is questionable (i.e. GDPR), no one will bother you as an individual company too much because any court would throw that charge out for being unreasonable.
"No one ever got fired for buying IBM" is just as valid today, it's just Microsoft. If you are a large company, there is virtually no alternative than the unholy triumvirate of Microsoft (Azure, AD, O365), SAP and Oracle (Java + DB) - deviating from that means lots of paperwork.
DirectX because steam defacto runs on Windows only for the vast majority of games, and not everyone wants a steam deck form
I can't think of any other S tier use cases tbh
Playing Arc Raiders now on Linux just fine, and several other new games. Not BF6 though, that requires you to basically install a windows rootkit.