yes it was explained a few chapters back but i cant remember the reason well though, i think he gave all his time and effort to his people and after his mother died his obsession with doing everything for his Kingdom grew so he became more like a machine than a human.
After his mother death he was obsessed to do everything perfectly, he overworked himself even thought the prople around him said he should rest, he baerly eat and sleep, at last he collapsed and fallen ill. After then he gave up the CPs position.
Thank you both!
Do we know why he handed over the crown prince position to his brother??