People need a strong leader. As Oriath bubbles over and spills into Wraeclast, the ragged and the hungry will look to someone to keep them safe from harm. For now, it is merely a matter of survival, but it in time, a true society will form, and someone must step in to rule.
A city is not built in a day, nor even a lifetime. Sarn was being cobbled together up to the day it burned. With so many hands involved in its construction, fractures and slips were inevitable. People would fall through the cracks. Factions would form.
Oriath didn't learn from Sarn's mistakes, but they cannot be blamed. The death of a ruler always has and always will throw an empire's direction into the wind.
With an Eternal Queen, this is a problem we will never have to face.