This is also the handiwork of the Great Angel Leader Ophelia. She knew that before Noah awakened, letting the outside world see the Holy Dragon's resting place turned to ruins would cause a terrifying shock.
Not only would it risk the collapse of order, but it would also lead the Dragon-men, who are as devout to the Holy Dragon as they are to the Divine, to form legions and launch a purge against the followers of the gods without Noah's guidance.
The consequences of this were too disastrous, so the Angels concealed everything until Noah awakened to guide his followers.
Now, a choice affecting the fate of millions, even billions of beings, is in Noah's hands. Peace and war hinge on the veil maintaining an illusory illusion above their heads.