Kusari has always been the least active house, because of the more complicated roleplay that you 'just have to like' to play it. Due to that roleplay new players didnt really feel attracted to it and if they did and did a few mistakes they got not taken seriously or even yelled at by the official factions, so that was a lack of innovation which made it boring to play after some time because it was mostly the same whenever you ran into someone.
Thats lasted until the end of .85.
With Gallia taking over Kusari in a, at least in my eyes not even remotely well done, plot most factions just got even more boring. There also was, at least gameplay wise not the slightest change.
The GC suddenly had achieved one of their goals when Samura was out of the government, the bd still had something to fight for, but their Samura goal also had been fulfilled.
The Hogosha had nothing to do that you couldnt do with a usual trader ID and the Farmers didnt have anyone to fight anymore, because less GC and BD bothered to log in.
KNF and KSP didnt really have anything to do either, so those stopped to be active as well.
Thats how I see the things that went wrong in Kusari, and I honestly dont see a real way to fix this mess any time soon to make it more active again.