Which is a lot like how the Ascians operated. They never resorted to anything as direct as mind-control or force to cause Calamities. Instead, they looked for places and peoples where they can push the existing negative sentiments far enough to cause chaos.
Meteion did it (probably) unconsciously, while the Ascians do it deliberately. I would say that this "pushing" did not only happen to societies which were already teetering on the edge, but also to societies that seemed stable enough, but where one strike in the right spot will expose a brittle weakness that brings it all crashing down.
Which again leads into how Hermes is the chief of Elpis, where he bends and ignores rules to his own benefit, and nobody calls him out on it (whether because he's the leader and nobody questions the leader, or if it's just because the rules don't mean much), and it is this rule-breaking unquestioned leader who is being nominated (by his predecessor in leading Elpis) to the seat of Fandaniel on the Convocation. Which he eventually got, despite being present at a major malfunction of a dangerous mechanism prompted by the alleged instability of his own creation's shared consciousness.
Our descent into Pandemonium shows that the Convocation can enforce the rules on the leaders of the facilities, albeit usually by simply wiping out the entire facility and starting over, which Themis feels is too brute-force a solution. Emet-Selch, as the official representative of the Convocation, decided that the memory wipe was considered unimportant and non-urgent, so evidently while the Convocation can enforce the rules, they chose not to in this case.
Also it's another sign of the dysfunction of Amaurotine bureaucracy that evidently Kairos itself has no records on how it was used, since none of the other Elpis researchers even mentioned "let's check Kairos to see where the malfunction happened". It's one of those cases which would, in the real world, get brought up in university lectures about safety precautions under the Powerpoint slide heading "every rule in the book is written in blood". But the Amaurotines, thanks to their sheer power, are almost always insulated from the consequences of their actions using that power.
Which does answer "why did Venat turn to Sundering". Venat didn't sunder as her first option: instead, she tried to convince the others not to turn to a deity to deliver them from their problems, and instead work themselves to rebuild Amaurot.
And while I admit to the irony of using the word "literally" for a metaphorical scene, the Amaurotines "literally" turned their backs on her, to pray to Zodiark instead.
If I recall, Midgardsormr was not the only dragon to flee, although he was considered the most powerful (both to flee and in general). It's just that very few dragons chose to flee, and to the dragons in the (recreation at Ultima Thule of the) Dragonstar, Midgardsormr's survival is the only one they'd heard of from us. If any other of the fleeing dragons survived, we might never know.On the dragons: In the quests in Ultima Thule, you find out that Midgardsormr was widely mocked for his decision to flee and that is why he was the only one t make the journey. Midgardsormr had the answer, for sure, but his answer brought him to Hydaelyn/Venat and away from the Dragonstar. His answer and hers were in synch. And the dragons left behind, who yes wanted to live before, experienced the horrors of a war that led to their young being killed and corrupted. Now, they have no interest in living, preferring to become as stones.
Also I liked that after the final MSQ, the sidequests in Ultima Thule had the recreations there start to live and hope again, like how the dragons realized that while their world was dead, they still had the power, however miniscule, to slowly bring it back to life.