This looks a lot like a joke-question, but whatever.
Well, technically it's possible to write an OS in React, if you're basically just running a browser and do everything inside that.
Since a lot of desktop apps nowadays are just repackaged versions of chrome with a single website in them, you might actually have a better user experience for /some/ use-cases.
But if you actually plan on doing that, please just make an browser-based OS that is a wrapper for this site:
Edit: I'm only answering semi-seriously because sometimes it's the stupid and laughable questions that foster new, maybe even completely unrelated ideas.