The Valyrians may be the most erratic civilization ever conceived. A sort of fantasy Mongol empire

>The Mongols discover that if you shoot arrows from horseback, you lose the disadvantage of being an archer
>They conquer everything in their path and kill trillions
>They never exert real power over what they conquered, they just kill a lot, are very scary, and demand tribute
>When a Khan dies, there's a nuclear explosion of civil wars and the empire disappears

>The Valyrians tame dragons, literally tanks powered by fire magic that disintegrate everything in their path in a yawn
>They conquer the Ghiscari, a slaver race who lived on the other side of the bay
>They conquer an empty stretch of land west of Valyria (?)
>They massacre the Andals (after most of them crossed into Westeros)
>It takes them 4,000 years to attack the Rhoynar (their immediate neighbors)
>The remaining thousand years they do nothing except raise slaves and excavate the foundations of their volcanoes
>All Valyrians die in the Firecaust

It's strange, because their empire was conceived with very decentralized power, what prevented a dragon rider from riding in his blood magic-powered tank, blasting off to Westeros (or wherever he wanted) and burning a couple of castles and returning to Valyria in time for the orgy with his sisters and dinner? They did pretty little for all they could...

Were the Valyrians canonically idiots?

>We can't make colonies on Sothoryos because... PEOPLE GET SICK WITH WILD BUGS AND PLANTS AND THERE ARE BIG ANIMALS!!
>There are cursed cities!!

Having dragons, and Sothoryos being a BIG JUNGLE, why not set everything on fire? The ashes fertilize the soil after the massive fire, and you can make colonies there to mine gold, gems, or whatever you want, and grow whatever you want in the fertile land. Assuming dragonfire doesn't disintegrate the cursed OILY BLACK ROCK cities (oil burns, by the way), then avoid them, or practice your albino blood magic against the cities or whatever you want.

Sothoryos was the continent to their south, quite close to Valyria, where no one lived (if people did, they didn't have complex societies that formed kingdoms or political entities). A virgin land with resources, and they left it there.