We creators of fantasy worlds often give WAY too much focus on the deep backstory of our setting. Now I want to make it clear, that you can run and play games set in Glorantha knowing nothing more than what is in the RQG core rules. If I didn’t feel like creating an adventure, I’d just grab the GM Screen and Adventure Pack and be off on my way.
Now I know the Arkat and Nysalor story is one many people are fascinated by, but remember it took place 1200 years ago. That’s like a Greek of 350 BCE telling tales of Perseus and Heracles. Even the Trojan War is closer to the present. So remember all the stories contradict each other, and likely nobody has a good accurate history of the time. The Gbaji Wars are the Trojan Wars of the Orlanthi, or the reign of Zahhāk as recalled by the Achaemenids.
The main reasons it is remembered are:
There are a lot of cool epic stories about heroes from that era.
For the Orlanthi it introduced the refined version of the Lightbringers Quest and so is tied into their biggest sacred tale.
For the Lunars, Nysalor illuminated the Red Goddess and so it is tied into their biggest sacred tale.