Koreans may not be a TOP 1 arabia CIV, but for closed maps it was an OP late-game civ on release of AoC.Koreans.
Anyway, it was a joke, they are not even the same developpers and back in the days to get the expansion you needed to buy a CD, no patches whatsoever...
The idea of having new civs OP comes with AK, after the forgotten civs had been incredibly underpowered and hated by most (remember the 3 i-s of bad civs Incas, Italians & Indians?), slavs were bad celts and magyars not really shining.
It was with African Kingdoms that they got a patch that really empowered them and they have been progresively nerfed. Incas are still top, but some years ago Indians were incredibly overpowered and no-one could win a game against them unless they had Indians too (I think they got slightly nerfed just during KOTD1, when they lost arbalest, but still killing). Italians had their OP condos for ~2 weeks and they changed that quite quickly, and slavs have been being quite powerful (not superdominant, but powerful) just until DE fixing farms.
Balance need testing, I hope next week we get our fix to steppe lancers and we will forget this madness (there will be another, dont worry)