I can't speak too closely too the article because I skimmed it. Ill probably try to give it another go later on. So forgive me if I miss the point but this was my take on your question...

But to speak of authors portrayal of his mother for some reason it makes me upset since there is no reason to make excuses. They could have broke the cycle or bettered her situation one way or another.

When I was growing up I straight up fucking hated my mom I think more than typical teenage angst. I loathed the way she treated our nanny. Not just with my mom but also my grandparents. The person I would confine with was with my nanny cause we both recognized how selfish and self righteous she was and how systematically it was unfair and hypocritical this whole nanny situation is. It really upset me to see my mom treat my nanny the way she did . Luckily, my mom did change and break the cycle and we have a great relationship now. Tl;Dr: my mom was a total piece of shit and I am not going to make excuses for how she treated our nanny, but she is better now and a more compassionate person.

As far as the childrens unwillingness to help I think there is a lack of cultural connotation in an Asian household where children are supposed to be subserviant to their parents. Any defiance of that in an Asian household is almost unheard of unless you want to be shunned or earn a good beating, especially when you are younger. This is just more of the cultural norm. At the same time family units are super tightknit.. almost like a Stockholm syndrome​ but to a lesser degree. I can empathize with the kids for not doing anything, but if they were grown adults then they should have taken matters into their own hands and face family backlash. That just my opinion though.