Mistress Alexandra knew that it was painful to ass fuck a guy with a strapon and that is why she did not want to feel guilty when she did it. So she paid this guy to agree to it and that way, she would not feel bad about doing it to him. The mistress had a great time doing it and she did not feel about what she did to the guy.
This mistress needed to humiliate and at the same time dominate this guy. The mistress did it because she felt that he needed to be shown how to fuck. The mistress felt that he did not know how to do it because he had fucked her poorly. So the mistress used a huge strapon to ass fuck him and after she had taught him, she made him fuck her again.
Madame S wanted her money back from this guy but he was not playing ball. She was disappointed in him and she had to force him to give her the money. So she ordered this guy to fuck him in the ass while she concentrated on fucking him in the mouth with a strapon. The guy was straight and it was therefore total degradation and humiliation for him to go through what he went through.