The questions I want EW to answer the most: WHY and HOW was the world sundered?

[Lauront]

At this point, I'm very much expecting a third party entity to ultimately be to blame for the entire predicament. Potentially the very same entity that caused the Sound. The writers have, thankfully, been pretty clear at establishing the nuance of the situation. Neither Zodiark or Hydaelyn are necessarily 'good' or 'evil'. It's all very much a matter of perspective. So, too, does that apply to the Ancients and the Ascians, the Sundered and the Unsundered. They all have their own goals, dreams, desires and a will to live.

I also suspect that the Warrior of Light will go the way of Azem and seek to find a 'third way' when it comes to solving the plight that is the Sound. Especially if the Final Days are indeed returning for a second time in the same form as before. Or, alternatively, perhaps the story will involve Hydaelyn and Zodiark being brought together in a state of balance - given that the Sundering has been described as an 'unstable state' by the writers themselves in the past.

Whether Venat is an antagonist or not, I suppose, depends entirely on a few key factors such as whether the Sundering was accidental or intentional.

My own personal hope is for the story to set aside differences, acknowledge each side as having understandable motivations and then have everyone come together to beat the Sound which may or may not be a Lavos or Jenova type entity in typical JRPG fashion.

Pretty much my hopes as well. I think in her faction's case, well intentioned but perhaps misplaced concerns were exploited to create an opening for the crisis's originating source to reassert itself. I have a hunch that it used that as an opportunity to take over Zodiark, once weakened, and in this final battle will attempt to do the same again but not just to him. Stories verging on how more potent beings such as the ancients could only but be destroyed or "deserved" it or somesuch are unlikely to appeal much to me, particularly when races like dragons seem to elude such treatment. Not like we have to sunder the elder dragons because of the great power their eyes hold. If age old grievances could be put aside between man and these alien, and very potent beings, so too can reconciliation be achieved between unsundered and the sundered fragments of their race.

I mean to be fair the convocation did also have time It can just be argued they used it poorly. The calamity of the unsundered world wasn't an immediate "Snap now were all dead" we know from “Debate and Discourse” that there was a large enough time for even the citizens of Amaurot to have lengthy discussions on the direction the world was heading. I previously made a post under the "Zodiark Good or Evil" thread but to sum it up is the fact that the situation was far too complex to binary define who was right and who was wrong. Amaurot had hours to spend but focused too much on their play book of parley that they went into overtime and Zodiark was the most realistic option to successfully save their people (To them of course)

We know that they researched the origin of the crisis and sought means to address it. While one can speculate that their time was used poorly, it's not really confirmed one way or another, anywhere, to my knowledge. At the time it was occurring overseas, and already then they were devising a solution to it. The situation may well have ramped up at an exponential pace. Considering the unique nature of the crisis, they were probably taking a very cautious approach to how to resolve it, because it could exploit their very mental faculties and let their innate powers run amok once it had done so. It is very possible that the crisis, if manufactured, was made to look as natural and difficult to separate from natural phenomena as possible, and only to trigger at the right moment - certainly, the fact that Fandaniel can reproduce this crisis even without creation magicks being available to the sundered, should raise eyebrows.

Your question leads me back to something else I personally hope Endwalker answers. That being WHY did Venat HAVE to be Hydaelyn? She was basically the "CEO of Hydaelyn" so why give herself up instead of leading her group after Hydaelyn comes into existence? The quest "Beneath the surface" shows that one of her compatriots implores her to not sacrifice herself and instead choose one of them. She immediately shuts that down by saying.

Venat
"You know as well as I that but few support our cause. Far fewer than they who place their faith in Zodiark.
If Hydaelyn is to stand a chance of opposing Him, I am the only one who might suffice as Her heart."

Why was Venat so special? Why did it have to be her and no one else?

It's why I think they may be aiming for a Yunalesca reference with her - similar belief in her methods and an insistence that her champion adhere to them. As opposed to them doing something like turning her into an outright villain, which so far I do not see as plausible.