This is cool - a 360 degree, zoomable image . . .
https://gigarama.ru/notredame/
When you look at the picture things don't seem too bad on the surface. The wooden roof was basically a waterproof cover over the stone ceiling. The stone ceiling is still mostly in place. Basically the 'cover' has burned away. Sure, it's an enormous amount of work to replace the roof, and who knows what the heat has done to the stonework, but it could have been a lot worse I guess. This helps to explain how most of the interior stayed in reasonable shape, and how much of the glass survived.
