Your question presumes that we were in control and presiding over all Lucifer did, his attainment of power, and the choices he made to arrive at his lofty perch, as well as supporting him and perhaps allowing and enduring mistakes and missteps along the way, and even for some time after reaching a pinnacle of progress that turned downward. What you are overlooking in your question is that Lucifer himself was a being within the Milky Way Galaxy Domain of Free Agency and Free Will and, as such, was largely on his own to make his way to aspire to a level of attainment, according to his own desire for growth and expansion, just as we outlined as being Creator’s Plan for this notion of greater possibility when unfettered by being on a short leash controlling extremes that could lead to trouble.
So Lucifer was entrusted as you all are to make your way. Eventually, there are karmic consequences for all, and this includes the angelics as well. Their greater power and reach comes with a corresponding hazard of having farther to fall, and enduring a more severe negative consequence for mistakes, and especially wrongdoing done deliberately to serve the self. So in the same way that you have your worlds, yours and the worlds of the extraterrestrials, who are now causing you great harm, the angelics govern their dominion of the Milky Way Galaxy to serve the beings present with all manner of services to assist them with their learning and growth, as emissaries helping them to stay connected to Creator in a quite practical way through obtaining all manner of support, including guidance, inspiration, healing, and protection. Everyone needs a mentor, everyone needs a good friend to be a source of help that can be relied on, and this is as true for angelics as physical humans or extraterrestrial beings.
So your description of Lucifer attaining a leadership role through a consensus is an accurate one, but the trust was conferred by fellow angelics and was supported initially by Creator as an opportunity for learning and growth, not expecting perfection but expecting that the growth and learning and attainment of greater and greater responsibility, being won through service and life experience in the role created by this new paradigm, would enable an improvement and expansion of possibilities, but with self‑restraint and a healthy and successful personal rebalancing to stay in alignment, and thus add to personal success as well as the collective success for all affected by everything Lucifer was responsible for. So he truly earned his position of trust in being an ultimate leader of the angelics for the entire Free Will Project within the Milky Way Galaxy as a whole.