Why is Loki considered the spark that ignites Ragnarök?

Core Q&A Expanded Answer

In the Destiny Cycle, Loki functions as the catalytic force that turns accumulated tension into open catastrophe. He is not the whole war itself, but the spark that ignites it.

Other Core Q&A Expanded Questions

How did the Nantuates, Veragri, and Seduni resist Roman control around 56 BCE?
Which Aquitanian peoples submitted to Rome after Crassus's campaign in 56 BCE?
Which northwestern Gallic peoples resisted Rome under Viridovix in 56 BCE?
Which peoples joined or supported the Veneti against Rome in 56 BCE?
How did the defeat of the Veneti change resistance in coastal Gaul in 56 BCE?
Why did the Veneti lead resistance to Rome in 56 BCE?
What happened to the Aduatuci after they surrendered to Caesar in 57 BCE?
Which Belgic peoples made their major stand against Caesar at the Sabis in 57 BCE?
What happened when Caesar entered the territory of the Ambiani in 57 BCE?
Why did the Bellovaci surrender to Caesar in 57 BCE?