I've been watching antitrust cases actively since the 1980s. I had to study historical antitrust cases going back to Standard Oil and RCA, in order to ensure compliance with a related consent decree When I worked at IBM. Each of the other cases had one thing in common: Both of the companies being charged were massively and obviously monopolies. There were many questions about whether they were behaving badly or really had an adverse impact on competition, but there generally was no doubt they had monopoly power.