This guy was insecure and lady Ayse did not want to deal with such a person for long. That is why she opted to humiliate him and dominate him as cruelly as she could. The mistress had fun making him a chastity slave. After he wore the chastity device the way she had tricked him to, he realized that he had surrendered control over his dick to her as she had the chastity key.
Lady Ayse was out to control this guy and she had to do it with her chastity humiliation fetish. She knew how to make the guy wear it and this time he thought that it was something which was meant to make things fun and saucy for him and her but it turned out to be something to control him and dominate him. She used it to control his sexuality and by extension him.
Lady Ayse was interested in chastity humiliation and that is what she ended up doing. But since she was careful on who she wanted to try it on as she did not know how it would end, she chose her ex as she did not care what he felt or what he thought about her. So she used her seduction prowess to make him wear a chastity device and then she teased him and watched as the device inflicted pain on him when he got aroused.