I think I understand the season 2 story now.
Exaltists threw everything they had at the Weifei region to stop the preclude production an make the hollow eat up the aerospace city.
But it wasn't enough because the locals had a super sword that turns a scrub disciple into a Voidhunter at the cost of their life.
Plus the exaltists realised the Aerospace city remained stable due to the nearby natural Porcelume ore.

So it was one giant war of attrition for little to no real gain. So they gave up an deviced some new stratgies.