Des2ny is Canon (Story Spoilers) (Destiny)

by EffortlessFury , Monday, September 11, 2017, 09:53 (2417 days ago) @ Schooly D

Blow up the ship, which is not a threat at all at this point in time.
Assault to take back the city.
Gault takes the light.
Final Showdown.

This bugged me too, but I assumed I was missing something.

The mission to destroy The Almighty tried to make it seem like the Sun was going supernova at any moment and we had to stop it. But with Gaul still on Earth and his entire army still in the solar system, surely the danger could not have been imminent.

But you destroy The Almighty and... it doesn't seem to matter much, least of all to Gaul. It's not like he was using it as leverage. The Almighty gets blown up and all that happens is Gaul's adviser mentions it in passing and the game continues as normal. The final showdown continues exactly as it would have if the Almighty had still been there, or if it never even existed.

The Almighty was sort of a contingency. "Test me and risk annihilation." The gang didn't know about Gaul's issues and how he was desperate to be chosen, they just knew they had to stop Gaul before he forcibly took the light. To make a move on the City they wanted to ensure Gaul couldn't just leave and pull the trigger on the sun.