https://www.nytimes.com/roomfordebate/2015/04/16/what-are-co...
This can be and has been widely interpreted. It does not have to mean maximizing profits to the exclusion of everything else.
I think one could say that one's "duty" is more about what is ethically required, however. I tend to think that, ethically, a CEO is required to maximize shareholder value. This doesn't mean that he needs to agree with shareholders about what that means, necessarily, and trading off short-term value for long-term value could be the right call.
I feel like sometimes "caring only about shareholder profits" is some kind of code for being greedy, when I think it's quite the opposite -- it's much greedier to spend your company's money for your own vanity, or to set up your next job, or to do favors for friends -- often the non-profit-maximizing activities a CEO engages in falls into one of these buckets.
It is also completely reasonable to say that it is in the shareholders' best interests that their company act ethically, and in accordance with the law.
"Fuck off, I know what I'm doing, and I'm not chasing short-term single quarter results" can easily be fulfilling that duty.
And the cases you bring up for fraud/negligence are very different, and pretty obviously not covered under running an enterprise in good faith.