Ehh this isnt really rocket science. If you take someone who is specifically focused on their own benefit over that of the company, and you have that person run your company... they are going to make choices that benefit them more than your company...
I wouldnt say CEOs arent worth it, but the incentives are completely perverse.
If it was the opposite, it would also not really be rocket science: "Good CEO's have immense values for companies. So of course companies would pay a lot more for those CEOs that do a good job -- it is worth so much to the company."
You can't really make useful predictions with that kind of reasoning.
The study shows how [over]compensating CEOs with stock options has a much more negative impact on their future stock price than [over]compensating them with cash. In other words, the more aligned CEOs' incentives were with the indicator of the performance of the company, the worse the company did.
I wouldnt say CEOs arent worth it, but the incentives are completely perverse.