It's just... every language is good in something else. XML is a medium for transporting data, like JSON, so the model. Html5 is great for displaying stuff, the view. C/C++ works best for doing the logic stuff, the controller.

Put everything together and you have the MVC pattern.
Well not entirely but just to make a point. It's pretty clear to me, I don't understand too well whats so insane about it.