Another reason could be revenge. If a wife discovers that her husband has been unfaithful or has treated her badly in some way, she might decide to cheat as a form of payback. For instance, in a particular story, a husband had an affair and his wife found out. To get back at him, she had an affair of her own.
One possible reason could be blackmail. For example, someone might have some incriminating evidence about her or her family and force her to have an affair. Another reason could be extreme financial pressure. If a family is in dire straits and she is pressured by someone who offers a solution in exchange for an improper relationship.
Another reason could be boredom. If her life has become monotonous and there's no excitement in her relationship, she might look for it outside. But these are just fictional reasons and not an excuse for real - life unethical behavior.
One reason could be lack of attention from her husband. If he is always working long hours and not spending time with her, she might feel lonely and seek connection elsewhere.
One possible reason could be his inability to handle the stress of having a sick wife. He might be looking for an escape from the difficult situation at home. Another reason could be his own lack of moral values.
One reason could be the allure of the new and different. The young male nurse represents something fresh compared to her regular life.
One possible reason could be that the wife is unhappy in the marriage. Maybe she feels neglected or unappreciated. For instance, if the husband is always busy with work and doesn't spend enough time with her, she might seek attention elsewhere.
One possible reason could be that she was not satisfied with her own relationship before the wife swap. The new environment and the different personalities in the swapped - in couple might have attracted her.
One reason could be a lack of emotional connection with her husband. If she feels unheard or unloved in the relationship, she might be more vulnerable to outside temptations. For example, in some stories, the husband is always busy at work and doesn't have time to listen to her feelings, so she may start to look for someone who can give her that emotional support.
One reason could be a sense of adventure or the allure of the 'forbidden'. The interracial aspect might add an extra layer of excitement that she is seeking outside her marriage.
Lack of emotional satisfaction. If a woman doesn't feel heard or understood by her partner, she might be tempted to seek that connection elsewhere.