Standard Oil: Its monopoly was already crumbling before antitrust action. By 1911, market share had plunged from 90% to 64% as competitors like Gulf/Texaco emerged and new oil fields broke its grip.
Carnegie Steel: Government intervention. The federal government imposed steep tariffs on imported steel, shielding domestic producers like Carnegie from foreign competition. Without those tariffs, cheaper British/German steel would have kept Carnegie’s dominance in check.
Southern Pacific Railroad: Government intervention. The federal government gifted it, through the Pacific Railroad Acts, millions of acres and subsidized loans. This state-sponsored land monopoly let it block competitors from critical routes.
Google. Microsoft. Facebook. If it weren’t for antitrust, there’d be a lot fewer cell phone companies or airlines. I mean, it’s harder to name an industry where there hasn’t been consolidation. The only thing stopping it is the law. Consolidation was basically illegal until the 1980s. If you wanted to grow, you had to compete.
Google was literally declared a monopoly by a court recently. Facebook and Apple both are oligopolies or monopolies in certain market segments. Apple has a monopoly on app store and on device payments. These things are bad enough that they’re being litigated.