The executives have to be paid large salaries by the shareholders so that they'll put shareholders interests well above those of company employees and customers

The executives have to be paid large salaries by the shareholders so that they'll put shareholders interests well above those of company employees and customers. This allows them to justify overriding their normal human connection with their employees, and replacing any tendency towards co-worker loyalty with shareholder loyalty. Of course that also justifies treating customers as poorly as possible - just not so poorly that they stop coming back (although if they can monopolize an industry, customers will have nowhere else to go - see broadband providers, etc.). This is a primary reason why investment capitalism is such a destructive economic system in the long run. Shareholders tend to want to extract as much profit from the company in a short a time as possible; the long-term health of the company and their customers is generally not their primary concern.