You live in a society where successful people aren't mean. That's different from the rest of the world.
Maybe a more accurate title would be "Mean People Fail in Silicon Valley"
But there are at least big chunks of the world that mean people don't rule, and that territory seems to be growing.
I wish more of the essay was devoted to evidence of this, because it'd be amazing if true. But I don't personally see any evidence that mean people are becoming less influential.
When you think of successful people from history who weren't ruthless, you get mathematicians and writers and artists.
One specific counterexample: Gauss was extremely mean. And not only mean, but mean to his family:
Gauss eventually had conflicts with his sons. He did not want any of his sons to enter mathematics or science for "fear of lowering the family name".[36] Gauss wanted Eugene to become a lawyer, but Eugene wanted to study languages. They had an argument over a party Eugene held, which Gauss refused to pay for. The son left in anger and, in about 1832, emigrated to the United States, where he was quite successful. Wilhelm also settled in Missouri, starting as a farmer and later becoming wealthy in the shoe business in St. Louis. It took many years for Eugene's success to counteract his reputation among Gauss's friends and colleagues.
http://en.wikipedia.org/wiki/Carl_Friedrich_Gauss
I feel bad pointing out a counterexample like this, because it's easy to cherrypick an example of a mean person here, a mean act there. More difficult to show a general trend. But isn't the difficulty of finding examples of nice people evidence that niceness isn't very pervasive, especially throughout history?