that's sort of nonsense.
take south dwi geography... you have madina island on the one side and fissoa on the other. (and paisly on the other sea trip)
let's say, fissoa has 15 (or 20 or 30, doesn't matter) regions to the east but only 1 city. its city is smack on the front line. it loses the capital only.. and what, auto lose as a realm?
makes no sense.
I suppose it's another conflict between the strategy and the simulation parts of the game. And I very well know Fissoa is f*cked by it's geography. Max population of some 15k :/