Why do the angels say fallen twice?
 
Revelation 18:2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.
 
Revelation 14:8 And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
 
Would it be for a similar reason that it was also said like that in the old testament?
 
Isaiah 21:9 And, behold, here cometh a chariot of men, with a couple of horsemen. And he answered and said, Babylon is fallen, is fallen; and all the graven images of her gods he hath broken unto the ground.
 
Is it because, like ancient Babylon, she is fallen from without and fallen from within.
She is overthrown by external forces, but before that, she is totally corrupted morally on her own?