A loI of people don't know about this and I don't know if they really went ahead with it (been away from everything Microsoft professionally just about three years now) but at the time they were pretty serious about the idea to build all Office apps in React, so (according to them) they could more easily build "great multi platform experiences" from the same codebase.

Why they thought it couldn't be done with the .NET stack they already had (this was after the purchase of Xamarin and Blazor becoming a thing, mind you) still baffles me.