Definition of a Blight:"D uring the Blight unnatural dark clouds shroud the sky, providing shelter for the sun-fearing darkspawn. They obscure the sun in the daytime and the moon and stars at night, and form a perpetual storm that can be seen from afar. Soundless violet lightning sometimes flashes at the eye of the storm. The black clouds offer hardly any rain, and the rivers run dry. These conditions alone lead to deterioration of plant life, including forests, crops and seaweeds. Children and livestock born under the Blight clouds tend to be small and weak, often deformed and susceptible to disease."
"The First Blight is arguably the single most devastating event in the history of the dwarven race. The empire came to its knees as darkspawn flooded the Deep Roads that connected the countless thaigs and cities."---"Thedas was nearly overrun and the dwarven race nearly extinguished."Only with the founding of the Grey Wardens in -305 Ancient (890 TE) the tide turned."
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"as most of the Deep Roads are sealed, communication lines faltered between the surviving kingdoms. Because of that, at -195 Ancient (1000 TE), each kingdom elected its own king while maintaining allegiance to the High King of Orzammar."
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"in an effort to save the race from complete annihilation, High King Threestone ordered the sealing of the Deep Roads leading to the remaining three kingdoms in -45 Ancient (1155 TE).[22] Within a decade the kingdoms of Gundaar and Hormak had fallen.[6] The last of the Roads are sealed in -15 Ancient (1180 TE) cutting off Kal-Sharok which is believed lost."
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"Even though the sealing of the Deep Roads significantly decreased the pressure on Orzammar, the darkspawn were able to find ways to breach them. For the next centuries, the kingdom was in a steady decline by losing most of its outlying thaigs."
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"During the Fourth Blight the dwarves of Orzammar assisted the Imperium in lifting the siege of Marnas Pell, however the Ortan Thaig was lost."
Then there are the comments from surface dwarves selling to Orzamaar that they are a life line. And the paraphrase quote I posted regarding what the dwarves said in the Winter Palace.
If the underground dwarves faced annihilation at the the height of their Empire due to the very First Blight, they have no chance of surviving now that they barely have two kingdoms that rely entirely and completely on the surface for trade and income. it was partially their in fighting that cost their people so dearly in the first Blight. so it is not confidence, but blindness, that guides them to insist on naming a King instead of immediately helping the Warden.