Re: The invisible hand will make it all better.
"Best interest" would be decided in the court proceedings. Short or long term would be part of that. Most shareholders these days seem to want short - part of the current problem with big business, especially financial ones.
If the shareholders just vote the execs out, the execs get to keep all their goodies. If the shareholders sue and win, they can claw some of it back and also send a message, not that it is attempted very often. (The shareholders generally being other companies whose execs are cronies of the first company's execs.)
The point is that even if a company is making vast profits, considering the employees' interests beyond the bare minimum requirements of employment legislation can only be justified if the board can show the shareholders that it benefits the bottom line - by law. This is the reality of modern capitalism which some of us with ethical tendencies - whether from religious belief or because we understand that humans are social animals - find repugnant.
When you do occassionally get management that understands that a happy, secure workforce is a more productive and profitable one in the long run, some glans of a beancounter (aka CFO) comes along and takes it all away to improve this year's figures or increase the dividend on his own shares.