> The board of a company must act in the interests of shareholders

I think you don't understand what this phrase means. In a publicly-traded company, "the interest of the shareholders" does not mean "whatever the shareholders want"; it means "whatever is best for the company." That means money.

It may be possible to be both profitable and moral; but if it isn't, the fiduciary duty obligates corporate officers to choose the profitable path rather than the moral one.

The easy way of looking at this is that there beyond complying with the law, there is no general obligation for companies to behave morally, but there is a general obligation to behave profitably. So it's not hard to see why they make they choices they do.

> It's entirely possible to still satisfy those requirements by building a sustainable and moral company.

It is, but it's a lot easier to be not sustainable and not moral.

No, it does not mean money. A fiduciary duty is a duty to manage money in someone else's best interests.

It's confusing because "fiduciary" sounds like you have to optimize for the mercenary interests of shareholders, but that is not true. Not every corporation is founded to turn a profit; what do you think the fiduciary duty looks like for a nonprofit?

The general obligation for the company to behave morally comes from two places: specific laws and the fact that its employees want to sleep at night. These are more powerful than a lot of people want to give credit for.

How are unsustainable decisions and practices working in the best interests of the shareholders?

> there is no general obligation for companies to behave morally, but there is a general obligation to behave profitably

What is that based on? I'd say there are certainly obligations for both.

The fact that some ignore those obligations - either obligation, for example when corrupt management stuffs its own pockets - doesn't make them less.