Fiduciary duty, in the sense you are using it, is a myth (most likely created to justify shameful but profitable actions from corporations). A few sources:
California Corporations Code section 309(a):
A director shall perform the duties of a director, including duties as a member of any committee of the board upon which the director may serve, in good faith, in a manner such director believes to be in the best interests of the corporation and its shareholders and with such care, including reasonable inquiry, as an ordinarily prudent person in a like position would use under similar circumstances.
Directors and officers of Apple Inc., incorporated in California, are bound to serve in a manner such that they believe to be in the best interests of the corporation and its shareholders.
If the directors and officers of Apple Inc. could determine that their shareholders have an interest in abstaining from the Chinese market for ideological reasons, they could (possibly) make a decision which would not serve the financial interest of the shareholders, but I find it unlikely that their shareholders would consent to that.
It's obvious to me that remaining in the Chinese market despite the CCP's suppression of liberties is in the interest of the shareholders. It is a huge market, and the other markets simply don't care enough about this issue to stop buying Apple devices and services on account of this concession to the CCP.
https://medium.com/bull-market/there-is-no-effective-fiducia...
https://www.dailykos.com/stories/2016/10/6/1578437/-The-Myth...
https://www.nytimes.com/roomfordebate/2015/04/16/what-are-co...
There is such a thing as fiduciary duty, but it's not related to the common usage of public companies needing to maximize profit for shareholders.