What is the wisdom behind the mother losing custody of her children upon remarriage, even though their father does not fear God and only spends on them by court order?

Love between a man and a woman outside the framework of marriage is forbidden because it contains temptation (fitna). Therefore, the questioner and her colleague must repent and sever the relationship. As for the custody of the children, it belongs to the mother as long as she does not remarry. If she remarries, custody transfers to her mother, then her grandmother. The wisdom behind this is that the mother would be preoccupied with the rights of the new husband, and the child might be neglected. The father has no right to custody if he does not fear Allah and is immoral, because one of the conditions for custody is not being immoral.