One thing: if someone else did it, they'd lose 100. Because of your effort, we only lost 5. That's what being competent means.
Without a doubt, the most important source of income is the net interest margin, and risk control that reduces bad debt risk is crucial.
You can check out the original article—it's pretty good. Overall, China has effectively shackled banks, reducing their profitability. The greater the responsibility a bank bears, the more constraints it faces, the less leverage it uses, the more cautious its style becomes, and the more it actively sacrifices its own profitability.
For consumer brands, only those with a competitive moat can convert brand strength into pricing power—and only with pricing power can they sustain high net profit margins. A brand doesn't guarantee high margins. However, another hallmark of a well-established brand is that it's harder to lose money; what worries most people often becomes an opportunity for them to buy in.