DTs problem has nothing to do with being "Dark". They wanted to make an entirely fresh start but also have to realize that if the world has literally gone through the equivalent of World War 2 (and to be fair, this went even further than WW2. It was like WW2 plus having a natural disaster occur that required over half the planet and the literal heart of the life stream to deal with), there isn't going to be a place on Ethyris that isn't going to be going through some kind of recovery. Tootsie roll land ain't coming out unscathed from soul annihilating song of the end turning someone who has even a moments hesitation in conviction into an abomination, especially after seeing "we have a graveyard of babies down there from trying to breed a super weapon".

And even if they were spared the effects of that, the economic repercussions from the other nations having to expend significant resources would cause all sorts of chaos for places like the one we are visiting. Forget rite of succession being relevant: people should feel lucky they even have a freaking capital city left. The only place that had any excuse to being spared is Solution Nine due to sundering shinanigans and not physically being a part of the source.