This guy though that he was the best thing to happen to this mistress' life and she had to deal with him as she did not want him to continue holding such silly beliefs. That is why she used her sneakers to trample him and crush his nuts. She also crushed his dick before she was done with him. He was put in his place and he never forgot it.
This mistress had a stubborn boyfriend and she did not like that very much. She felt that she needed to change him and make him learn to do things in a different way. And he needed to listen to her. So she used her trampling fetish to punish him and in no time she had managed to make him feel pain and regret the things he had been doing. He promised to change.