I don't feel like the Sundering is something that just happened, personally, and rather think it's something Venat and her followers may have specifically engineered Hydaelyn to be capable of with the intent that "weakening" the world and its people would prevent the Final Days from ever happening again as it's heavily implied to have been a product of the Ancients' own folly.

Emet-Selch and the other unsundered thus far seem like the only reason that plan didn't pan out in the end...which makes me further question how they managed to escape an event of such a scale.