The decision here, in how to deal with the fallen angelics, was initially a joint one because the angelic realm was directly in the line of fire with that fall from grace, and were interacting personally with those increasingly self-corrupted, and influencing one another to fall further in their disarray with a lowering of vibration and the discouragement it brought, making it more and more difficult to return to divine alignment. So it was Creator’s Plan for the angelics to patrol all of the contents of the Milky Way Galaxy and help to keep things humming, so to speak. When Lucifer turned away from the light and led his cohort of angels on a downward spiral, it was countered by an outreach from Creator as well as the angelics who were still in divine alignment fully. But despite many attempts, the fall from grace continued and worsened and it was only then that a decision was made finally by Creator to say, “Enough is enough,” and withdraw life support because that was appropriate, given the quite long-standing descent into depravity indulged in by the fallen angels with no sign of an awareness or ability to self-correct, even after many attempts to heal them.
This is the risk on display of having free will and free agency—each being must make up its own mind what it wishes to do with its energy. So the perspective you hold about who you are, who you are linked to, and might have obligations to or be dependent on, will determine entirely what happens next and how things unfold for you. If you get out of divine alignment, this creates a distortion and it is difficult to regain the high ground you left behind. So all can undergo a fall from grace, and this is routine in physical existence, that one will be challenged and have times of being mistaken and misguided, and even corrupted by bad examples and influences. So the key is to have a way to receive healing and be restored once again to a high level of functioning that is in divine alignment, and can make you invulnerable.
The expulsion was approximately as you describe because it was clear at a certain point that severe damage had been done by the fallen angels, who turned away from love and light and were corrupting the Anunnaki severely. That continued conduct is what earned their fate as a karmic rebalancing, that eventually they were cut off from life support, which was a fitting punishment for, in effect, destroying the lives of so many other beings from the corruption they caused.