Classism in Elderling society? (spoilers RotE books incl Blood of Dragons)

['thul]

An eruption of super-volcanic size will hurl enough ash up into the air to clog up very large regions. Dragons generally lived in one main region, so while it was not enough to cover entire atmosphere in a layer of life-killing ash, it was enough to slay essentially all dragon-kind. There is one dragon that escaped, but no indications of any others. (that excludes the cocoons)

Such catastrophe will not give anyone time to run (or in this case, fly) away. When dragon-kind essentially became extinct, Elderkind also expired. Elderlings are, after all reliant upon dragon-kind to exist.
It is however not unlikely that elderlings were a bit aloof when compared to regular humans. For a good part they did not use scrolls, but memory stone. Due to that, a lot of their knowledge became inaccessible upon their disappearing. combine that with the fact that people will abandon higher learnings in the face of disaster, and you have ample reason for Elderlings to quickly pass from common knowledge. in the time period around the Elderling demise only a very small minority had knowledge of the reading arts, and most history was passed down orally. within some generations (5-6) any oral stories of Elderlings would have become extremely distorted, eventually turning into fairy tales for all except those few in the nobility that can read the few historical texts written down.
Since the Elderlings lived apart from the majority of humans, and quite far away from places like the six duchies, none even thought to investigate their homelands after such disaster. They had no need to contact them, and the common folk had not the means. Thus what few Elderlings that may have survived passed away while humans elsewhere were oblivious.

If you have no elaborate knowledge, then you simply cannot recreate something fully. Combine that with the fact that you need dragons to create Elderlings, and you have ample evidence why their society could not simply be rebuilt by anyone.

The fact that some cities survived while others did not, can be explained by their location. The coastal elderling cities were sunk in the seas, the midland cities became the rain wilds, and the mountain cities were too far up to sink fully. They may easily have been located much higher up, but there is no way to prove that. The entire continental plate that contains the rain wilds most likely sunk far down, or perhaps even was impacted from behind by another plate, lifting its rear up and sinking its front. that would explain how things shifted. such tectonic impact would also explain the quakes.