I think you're wrong, Chris.
The value of any asset is equal to the entire future stream of income produced by that asset, with each future slug of income discounted to the present by the appropriate discount rate. "Maximizing shareholder value" means maximizing (the present discounted value of) the entire future stream of income. Maximizing the next quarter's earnings is NOT the same thing as maximizing shareholder value. If a corporate manager sacrifices future earnings for a one-time bump in current earnings, the stock price should decline because that does not maximize shareholder value.
Here's a good example: there is empirical research showing that corporate managers sometimes change discretionary items--either operating items like R&D and marketing expenses, or accounting items like depreciation and write-offs--in order to bump up their earnings temporarily, especially just before they retire (and especially if their pension depends on the accounting earnings just before they retire). And there's empirical research showing that their company's stock price declines when that happens, because at least some investors see through the charade.
That doesn't mean corporate managers don't make bad decisions--but it does mean that "maximizing shareholder value" is the same as making good decisions from a long-term perspective, not a short-term one.