Monica had mentioned that long ago, and Khan fully understood why.
Princess Rachel Montares was a far better fit for Khan. She was a successful and prized Princess, and their union in marriage would bring two noble families closer, creating a super force that could affect the power balance in the Global Army's upper echelons.
Time also wasn't on the nobles' side. Khan seemed to grow stronger and more popular by the day, so it would come to a point when even Excellencies would struggle to have any influence over him.
That had actually already happened inside the Nognes family, but the other nobles only had relatively accurate hunches. They knew something significant had occurred before Khan's departure, but the Nognes would never publicly disclose that.