A lot of the concentration of wealth comes from the fact that economically there is capital, goods, and people. We made it super easy for capital to flow around the globe, moderately easy for goods to flow around the globe, and difficult for people to flow around the globe.
An Apple phone made in China, sold in South Africa, still sends money (capital) back to the US. This lets a few people gain extraordinary leverage at the expense of the lower ends of the curve in the United States who have seen their jobs shipped overseas.