I think there is something that happens to everyone or majority of the people. Some people call it emotional trauma. You know that there are times when you will experience something that is above your age and the next thing you can do is to act in funny ways.
Before the King left his palace, he was in his right senses. Even though he was not happy, he was still doing well. He was still acting well despite what his wife did to him.
But something changed. When he and his brother went to seek Allah to know their fate, they met a genie and a lady. They had sex with the daly and gave them one of properties. This is where their mentality changed. When they got home, they became weird and they were not like they used to be.
That was why he had to cut off the neck of his wife. I guess he did that out of frustration and the emotional trauma that I mentioned earlier.
He even did even worse by sleeping with the girls in the village and killing them when he is done with them. A sensible person will know that there is something wrong with the King.
I hope to see what comes out of the King and Scheherazade