In most corporations the salaries of executives are set by a group from the corporations board of directors.
Conclusion (clearly = opinion)
The expectation that having a board of directors set executives' pay will prevent excessively large salaries is based on poor reasoning.
Evidence (after all)
Most members of a board of directors are themselves executives at some other corporation and can expect to benefit from setting generous benchmarks for executives' salaries.
Evaluate
How do you determine the salary of a CEO? Can't she potentially make her salary whatever she wants it to be, since she's in charge?
Yes, but that would be bad for the business overall. The business might need to pay her a lot to retain her talents, but they don't want to overspend, or else that cuts down on profitability.
The solution? Have the board of directors, rather than the CEO, set the CEO's pay. The idea is that the board will pay the CEO only what she's worth. The board members are incentivized to make the company as profitable as possible, so they will pay the CEO the least they can get away with.
The problem with this method, our author points out, is that the board members aren't just incentivized by making the company as profitable as possible. They're also incentivized by wanting their own pay to be as high as possible. They are CEO's at other companies, and they have boards of directors deciding on their pay too.
So giving this CEO of company X a higher salary helps shift industry expectations of what a CEO should make. That could lead to the CEO's sitting on this board to be awarded higher salaries in the future. Their boards of directors will think,
Goal
So our author is saying this common way of setting executive pay might fail to restrain CEO pay because ... members of the board have a personal incentive to make this CEO's pay very high.