The way I see it is all about power. The uncle and Ilay use Tae to get rid of the other general trying to steal Tae's brother's weapons plans and Tae feels betrayed. He also remembered his uncle had been on bad terms with his father because he took Tae's brother with him for weapons development. And Shinru may find out about Ilay and Tae's sexual relationship and come to make absurd demands. I'm pretty sure it was Ilay who spill the tea. But the translation is a bit confusing.