I think this merely reflects the belief (a mistaken belief, according to some data) that a "great CEO" can make or break a company, and can make huge differences in the bottom line. Companies that don't have those huge pay disparities, and the data linked in the original article, seem to indicate that belief is not true.

We have developed a tolerance for executives being paid extravagantly just in the past generation, or so. It wasn't always the case, and it is at least as much a function of what people are willing to accept as what the market necessitates.