The summary is that the Chicago school of Economics promoted the idea that in a competitive market, predatory pricing is not possible. Thus, when you see an industry structure emerge (e.g. duopoly), you should assume that it is an efficient competitive outcome. After this, instead of focusing on market share percentages, antitrust authorities began to focus primarily on consumer harm (which is much more challenging to show in court e.g. for predatory pricing, you cannot only argue that your competitor has very low prices right now, you also have to prove that they intend to raise prices once they achieve monopoly power).

Given the current makeup of the court, it seems extremely unlikely that the justices would overturn this precedent.