Answer:
God only cast out one angel which was Satan himself, but at that time he was called Lucifer. Lucifer was known as the angel of worship and praise in heaven. But soon he became so proud and arrogant that he wanted to take the place of God himself. That is the reason he was cast out of heaven and also a third of the angels followed him out of ignorance but they cast themselves out of heaven!!!!
Actually, Bible scholars agree that a third of the angels were cast out with Satan:
"And another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.4And his tail swept away a third of the stars of heaven, and threw them to the earth . . . " (Rev. 12:3-4).
"And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him," (Rev. 12:9).
Angels were referred to as the stars of heaven, and Satan is often referred to as the morning star because it shines brighter than all the other stars, but disappears at night.