This guy was new and mistress Iside wanted to test him and find out whether he had what it took to work for her and be with her. That is why she chose to test whether he could follow instructions as well as lick her feet and her boots. He seemed smart and he understood that what he was being asked to do was a test so he did not ask questions. He just did it.
Mistress Iside was disappointed in the way this guy behaved. And she had to degrade him to teach him never to do it again. In effect, she knew that she had to control him and she did so using her boots femdom. The guy was shocked at the turn of events but he did not have a choice other than to do what he had been ordered to do. He learned to fear her.