Is a man considered to be at fault if he divorces his wife after discovering that she had a previous relationship with someone else before their engagement, even though he is certain that she no longer communicates with that person after their engagement, and she admits that she no longer loves her past?

Every human being has right and wrong actions. Fortunate is the one whose good deeds outweigh their bad deeds and who hastens to repent when they err. As for the pious, when an impulse from Satan touches them, they remember and are enlightened and repent, whereas the astray persist in their misguidance. Your wife's past, from which she has repented, is not a convincing reason for you to separate from her. You must close this chapter with her and not hold her accountable for something she has repented from. You should hold onto your wife as long as she is righteous and upright with you.