When your reason for divorce is having an unfaithful spouse, it will feel that you were forced to divorce, and therefore, you should get more from the split- to make it fair. This was not your idea after all, and if they had not been unfaithful, you would not have been forced to end the marriage and embark on this thorny path of divorce. Why should they get half when it was their fault?
Divorce as many people experience it at the beginning is more of an escape from an unhappy present, rather than a run towards a shiny future. Some say that they have no idea what their future will bring, but at that moment, they cannot accept the present.