The article describes how people overwhelmingly get hired through favoritism (that is, they get hired because of help from their social network) and this favoritism winds up discriminating against Blacks.
The great Fran Lebowitz pointed out the same phenomenon many years ago in her excellent essay about race:
... not only do white people own the playing field but they have so designated this plot of land as a playing field to begin with. White people are the playing field. The advantage of being white is so extreme, so overwhelming, so immense, that to use the word "advantage" at all is misleading since it implies a kind of parity that doesn't exist.
It is now common ... to see interviews with up-and-coming young movie stars whose parents or even grandparents were themselves movie stars. And when the interviewer asks, "Did you find it an advantage to be the child of a major motion-picture star?" the answer is invariably "Well, it gets you in the door, but after that you've got to perform, you're on your own." This is ludicrous. Getting in the door is pretty much the entire game ... That's how advantageous it is to be white. It's as if all white people were the children of movie stars. Everyone gets in the door and then all you have to do is perform at a relatively minimal level.