I only quoted a small portion of what you said. I’m not trying to take it out of context. It really isn’t intended to be a hyperbolic scenario. How it actually plays out is is up to someone who is a writer (not a programmer) - but most of the foundation is from this quest:
https^://www.wowhead.com/quest=52955/tyranny-of-the-light
In essence, the Lightbound Draenei in this alternate Draenor are led by Yrel and are… basically… exterminating anyone who disagrees with them.
"Brothers and sisters,
Decades have passed since the last vestiges of the Legion were driven from Draenor. We could not have accomplished this noble undertaking without the help of the orc clans, united as the Mag’har.
Our fondest wish is for all the people of Draenor to remain unified in purpose. Sadly, this dream is not shared by all of those who once stood beside us.
Many noble orcs have embraced the Light. Exarch Hellscream has been an example for his people to follow. Yet sadly, his own father resists the true path.
I believe with all my heart that the Mag’har are destined to join us as servants of the Light. But first, they must be taught to trust the naaru as we do.
The Light Mother has blessed me with visions. I know that one day the Army of the Light will march across the Great Dark Beyond and bring order to countless worlds.
That bold future begins here. With us. We must make Draenor whole again.
I call upon you all to ensure that the future promised by the Light Mother is fulfilled. Purge the infection that prevents Draenor’s heart from being whole.
The Light will forge a new future for the orcs… but first, we must save the Mag’har from themselves.
No more division. No more defiance. In the Light, we shall be one."
Yrel is one of the folks leading the army of genocidal light. Turalyon was a member of the Army of the Light.
After witnessing Calia as evil, Anduin turned into a Death Knight, and Bolvar turned into the Lich King, then once freed from that burden joining the Forsaken to aid the undead, Turalyon feels the balance of good and evil is off. The Alliance lacks the power to fight the Horde and/or push back the tide of the curse of undeath (especially with the feral Scourge joining the Forsaken). He calls on the Army of the Light to help.
Shockingly (sarcasm) they go further than anyone wants (just as the Prime N’aaru did to Illidan). Then it’s just a matter of who gets to do what. Eventually the floating chandeliers get beat back and we stop a colossal quasi-religious purge.
The army isn’t from the Alliance - it’s mostly made of Draenei - even though the Alliance leadership would be responsible for “inviting them in.” And while there’s some acceptance to them initially - they’re not under the authority or control of the Alliance, so it’s not like Turalyon gets to tell the N’aaru what to do.