Confusion (of the highest order) about Venat and Sundering

[Antoine_Lenheim]

Copypaste from Wiki:

Venat, who knew the true cause of the Final Days, opposed the Convocation and led a faction that sacrificed themselves so she can become the primal Hydaelyn. She used her ability of sundering beings to weaken Zodiark enough to imprison him within moon, simultaneously splitting Etheirys and most of its inhabitants into the Source and its thirteen reflections.

So, uhh, she wanted to stop sacrificing people by... sacrificing people?.. That's some twisted logic right here lol. I mean, yeah, proportionally speaking sacrificing a faction is nothing compared to sacrificing another half of the population but do we really want to start putting lives of the people on the weight? Why it was worth it? Were there no other way around?

Another confusion is, how come sacrificing HALF of the population is only enough to summon Zodiark and halt the spread of Oblivion Song but sacrificing of a faction is enough to literally give Venat godly, maker-like powers and abilities to impison Zodiark and manipulating of UNIVERSE and planets itself, sundering the world into 13 shards. How did she become so powerful?! Was that faction consisted of, like, super powerful ancients and such? That sacrificing mere dozens? of lives was enough to overpower combined effort of HALF the population?

So weird.