A change made through court cases in the mid-century. Basically the result of a neoliberal ideological campaign that first normalized the feduciary duty concept in the business world before forcing it on board rooms through the justice system. Before that, boards of companies could make decisions on ethical grounds and not just fiscal grounds. Today, that precedent has transformed boardrooms into terrifying financial automatons.

https://en.m.wikipedia.org/wiki/Dodge_v._Ford_Motor_Co.