A speculative bit of definitely-not-canon here, but I was wondering what people thought about this little twist to the setting.
So, you have the endless sea of Chaos, and you have the world as a bubble of not-Chaos within it. Things within the world which are of Chaos want to unmake the world to get back to the sea.
Now, everything in the world was Chaos once, But now it isn't. So perhaps part of the process of transitioning from nonexistence to existence involves the stuff being brought into existence being purged of Chaos? Those things encountered within Glorantha that are of Chaos are entities which either failed to properly purge themselves of Chaos when they were brought into being - the Unholy Trio might qualify as such - or which were brought into the world without any proper attempt to purify them whatsoever (Wakboth would be an example of that).
Some of the legends of the God Time might be understood as the nascent Gods undergoing the process of purging themselves of Chaos so they could be fully manifest in the world - take, for instance, the Initiation of Orlanth, in which Orlanth and most of his siblings succeeded but Ragnaglar failed and thereafter ended up part of the Unholy Trio. Maybe the "evil" uncles in that were just trying to purge Orlanth and his siblings of any vestiges of Chaos remaining in them. Orlanth's hatred of Chaos may in part come down to him taking offence at entities trying to get away with shirking the work of becoming fully real that he and (most) of his brothers did. The apparent paradox of Yelm being associated with Illumination but not apparently having Chaotic affiliations himself may be down to Yelm retaining some understanding of the nature of Chaos after being purged of it.
In the Dawn Age the Council were not fools - they weren't deliberately trying to make Gbaji happen. But in their enthusiastic reverence of their new God they failed to make him purify himself of Chaos, or couldn't bring themselves to force him to, or never realised that it would be necessary to begin with, so the Gbaji Wars happened. Likewise, the Red Goddess successfully brought something new into the world, but either chose not to or couldn't purge the Red Moon of Chaos - perhaps she found it simply too useful to give up. Perhaps the White Moon, once you get past the White Moon Movement's propaganda, is really what the Red Moon was supposed to be if it had completed the process of entering existence properly - or the Hero Wars are in fact that process of purging which will allow the White Moon to be born from the Red, free of Chaos.
The big problem the Lunars have is that they are wrong that Chaos is a necessary part of existence; it is a necessary precursor to existence, that becoming fully extant requires one to give up. A thing that will not let go of Chaos is a thing which will never fully be what it is supposed to be. The living tainted by Chaos will live a life dedicated to undoing life; the undead raised by Chaos are dead things failing at properly being dead.