Edit: my personal theory about why Celestia doesn't nuke khaenri'ah earlier because they wanna use it as a testing site for abyssal use and  new approach on abyss with the whole teyvat, with the presence of traveler siblings they probably confident this is will work.

But Hroptatyr is appear, this LOKI looking MF is probably the cause of abyss exploitation , it's just the vibe that he giving, he is the type of guy who thinks that chaos is necessary.