>>96582178
It ain't the Orks making that infrastructure. It's grots all the way down. Maybe they have a weirdboy to write up the "blue prints" but otherwise it's slave labor all the way down.
Those orkish empires are just arguing over who's the biggest at the moment. Once they figure out who the boss is, they are going to pick up and go out on a WAAAAGH because fighting other boyz is fun, but not as fun as fighting other races.