he's turning Wano into a weapons developer, opening new factories in Kuri
Also remember, Orochi has HIS OWN OTHER DEAL with Kaido. They aren't like just friends or anything. The old hag said orochi gets backing FOR MAKING WEAPONS. Kaido would have kept backing him if he had no weapons. Like what exactly was Kaido doing for five years then if he wasn't gaining anything from wano. Why did he fight Moriah in that time for a place that's providing him with nothing.
Orochi had been in cahoots with Kaido for Three years already at that point and the factories were there at minimum for one year. The narrator said Nothing changed. He didn't say things went back to how they were three years ago. He said NOTHING CHANGED.