IMO, Goodhart's Law[1] "Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes" or "When a measure becomes a target, it ceases to be a good measure" is a big part of it. As soon as stock price is the primary target it ceases to be a good measure of the actual value of the company, management will try to game the stock price at the expense of the underlying value.

[1] https://en.wikipedia.org/wiki/Goodhart%27s_law