Note that a virtual DOM is pure overhead if you already have a real DOM to work with.

That's kind of the ignored superpower of a framework like React, which makes the virtual DOM the authority: there might be a DOM, but there also might not be. Whether the virtual DOM reflects to a real DOM, or native UI, or Qt, or an ASCII terminal interface, it doesn't care.

This is also the part that most web devs have the hardest time with: React (and some other frameworks) are not web frameworks. They really are just UI frameworks, that happen to (also) work in a browser. Even if they were original born out of a web need way back when.