Because there is a lot of struggle 2 survive in d university. To survive accademically, financially and even 2 survive d cult members. So d man may believe dat since he is not there, d lady can easily identify with another guy both 4 security and provition who she may in-turn (after d course of their study) may not be able 2 abandon.
Its out of experience. Av seen men who lost their wives to other men upon giving them university admission. Part of the reason is the fantasy of being with a person of equal educational status. Yet its not all women that does that