User blog comment:Timeoin/Dragonborn Screenshots/@comment-4043978-20121119225120/@comment-1600847-20121120005706

"With the disappearance of the god Vivec, the Ministry became unstable."

Disappearance.

He was kidnapped and taken into Oblivion. That caused The Ministry to fall, which caused Umbriel to create the Ignenium to prevent it falling, which caused Sul to destroy it to avenge his dead wife who's soul was in the Ignenium.

I don't know why there aren't any articles on Infernal City on this wiki, but it's all in the book. Read it. Bethesda declared it cannon.