When people hear that a mother is abusing their children, especially if that child is a boy, it's not taken seriously whatsoever. If the child were to speak out they would get these types of answers back:

"Don't worry, your mom loves you and wants the best for you"

"Stop complaining, shes your mother"

"Why are you so ungrateful? You need to respect your mother. She gave birth to you"

But if the abuser is the father, it's taken 10x more seriously compared to if the abuser is the mother. Now if the child were to speak up about this, they would be getting so much more support from other people. Some might even go to the extent of calling the police to save the child from the father. But if it were the mother? Nah, the child is immediately assumed to be a spoiled brat, disobedient, etc.