Larian shows the Divine as a flawed man, which isn't anything unexpected, because he started as a mortal, thus a person, who makes mistakes. We also find out, that the Seven Divines/gods were as flawed as Lucian.
Yes, man are flawed, that why elf should have been chosen as Divine One and not all three possible human candidates (marked ones). No dwarfs, no lizards, not even imps. What a bunch of racist gods.
I'm not sure about the Elves though, is there any evidence, that they planned an uprising, or that Lucian had a reason to believe they did? I always thought they were just collateral damage, the Black Ring was close to them, so nuking that area with Deathfog would hit the Black Ring and well "sacrifice" some Elves in the process. A necessary evil so to speak.
Spoiler warning : some of the elves wanted to save the world from corrupt and flawed humans and even Mother Tree was backing them up (she is demigod with potential to reach a real divinity, if she consume enough source). Shadow Prince proposed to Lucian just kill the mother tree, but he decided to genocide most of the elves instead. Saheila is actually warmonger and wants to restart the war, but she needs to kill mother tree first because MT no longer wants it and can stop elfs from doing that.
