It is said that, having been given free will in the moment of their creation, the orders of angels had the capacity to make choices. Among these was that of entertaining pride and ambition.
It is said that one even went so far as to ascend in aspirations to enter heaven by right of her own will and become the equal of god, to usurp his prerogative of creation, and to take a station above all other angels and for this, god banished Lucifer from heaven, throwing her down into hell and with her fully a third of the angels, being those who had followed in the footsteps of her rebellion.
These became numbered in latter days as demons under the dominion of Satan.

... What if That is not exactly how it happened?