…that going by the Chronicles, a relevant part of Arthas’ motivation was to create a world, united by his dominating death magic, which could stand against foes like the Legion without infighting and mortal flaws? What an interesting an unique idea.
"A world ruled by the undead would have no more injustice, no more wars, no more mortal flaws. Perhaps most importantly to the Lich King, he believed his Scourge would be far more capable of defending Azeroth against threats that would try to conquer it. He had observed the awakening of C’Thun and the Burning Legion’s attempts to launch other attacks on Azeroth. Neither the demons nor the powers of the Void would rest until they controlled the world. A fractured world, constantly beset by skirmishes between the Alliance and the Horde, simply would not be prepared for another incursion. " - Warcraft Chronicle vol. 3, page 172
Oh well, it could have been better explored instead of tagged on later, but that happens. But that’s just a totally unrelated tidbit, and not that important. I mean… it’s not like they would do that again, right?