Quote Originally Posted by KariTheFox View Post
Was it?
Yes, all life and the Lifestream itself was being killed. This isn't exactly consistent with what we see in Endwalker, but it was their situation then. The devastation was probably exacerbated as well due to the Ancient's creation magicks being hijacked, creating things like endless rains of fire and tidal waves engulfing the land. Regardless, by the end we're told the planet was completely ravaged and all but lifeless, which is what led to the second sacrifice to restore it and restart the Lifestream.

Besides, I think that misses the point. Zodiark isn't an engine you can just throw biomass at until it does what you want.
That is in fact exactly what Zodiark is. He needed massive amounts of aether to do the massive things they asked of him, and the Ancients were the biggest (and at that time only) reservoirs of aether around. This metaphysical, religious aspect you describe, where they needed to give up something intangible or spiritually important, is not part of the equation. It's very much true that they revered Zodiark given he was their only hope, but where you got the rest of this idea I have no clue.