The great lords who plot against Javan have accumulated more power than the young king has and are less accountable for it. Accordingly, the theme of King Javan's Year seems to be "Absolute power corrupts absolutely."
Or even more dismally, it might be "Age and treachery will always triumph over youth and idealism."
The overall plan of the Gwynedd novels requires this type of ending. As one of Kurtz's admirers reminds us, two hundred years is not actually a long time as "dark ages" of repression go. Compared with the centuries of Christian suspicion of the Jews, or the millennia of male bias against women, a turnaround after a mere two centuries seems magical itself. Nonetheless few humans have that long a perspective. In having hopes that go beyond their own vulnerability, some characters project a more positive theme.
Javan himself finds solace from his political problems...