Although you are already gone (lol). I mean, maybe it's like that and Kouen has had his focus on the Bayue. And I would say possibly on Qi as well. There also was the matter of the royal succession, the internal problems with Karin and Rien as the two leading figures tasked with a "rebuilding" phase for Chu.
But...it's probably also a plot thing, lol. Given the immense problems Riboku has given Qin, if Hara had Kouen also thrown out there before "his" time, possibly even allying with Riboku, Qin would be in unbelievably deep shit.