> Board operates behest of stock owners, executives operate behest of board

These are often both weak signals, though. They'll govern very high level decisions, but all the day to day is inside the company. Just as I want a return on the money in my bank account (as I was promised) investors want a return on their money too, and as you say, the executives and board should care about making sure the people who put money into the company are getting a decent deal out of the arrangement.

People have always way overstated the power and scope of “fiduciary duty.” It doesn’t mean you have to redline your company at all times to maximize every single penny in the short term at the expense of all other considerations. That’s just a cultural thing we do in the US by choice