@Legion. My man, you are just too wrong here. I am not in habit of calling someone as wrong or right but you have clearly missed the first chapter.
In the first chapter, he died in a ball of flame while laughing with glee and happiness. He died and when he got reincarnation he happily renounced his old life too, society tell us to care for our family but he gives a damn about it. For him, magic is the only thing in the world.
Guys like him are usually called as psychos or sages throughout the history depending upon the era.
And also, if he did not understood the miasma then he would not have been able to defeat the majin. And if he shows his power everyone will call him to be the king.