Destruction was his only power
His power was destruction, which meant that he attracted miasma, the evil energy of the world. We saw when Stella first arrived that he was surrounded by the stuff. People literally got sick cos of it. Someone surrounded by miasma couldn't be king. He is only able to wander around like he is now due to Stella's purification
Also, he has no interest in being the ruler. He said he wants to support his hardworking brother who is more suitable. My guy is enjoying having the benefits of royalty without the strict responsibilities of leading the country. Waking up late, not wanting to do much, etc I love that for him too. He can be supportive and still find happiness with the FL without taking over a position he’s not actually interested in
I’m so confused as to why the first prince isn’t crown prince