[gamblor956]

Antitrust law focuses on the restraints of trade. Companies that are minor players in the market have been successfully pursued for antitrust violations, because it does not require a monopoly, or even market dominance. Monopoly law was the origin of antitrust law, but today is merely a subset of it. (For example, bid rigging, market allocation, and price fixing are all antitrust violations.)

Antitrust generally requires a substantial market position, and the use of that market position in one of a number of enumerated anti-competitive manners (the list differs between the U.S. and E.U.). One antitrust violation both the U.S. and E.U. have is the abuse of market position in one market (i.e., mobile devices) to anti-competitively establish market position in a different market (i.e., streaming music).

Apple has approximately 1/3 of the EU market for smartphones, which is a substantial enough market position for a single market position that antitrust concerns come into play. (Legally, the comparison is not Apple vs Android; it's Apple vs Samsung, LG, Huawei, etc.) Note that Samsung, etc., would have similar antitrust concerns if they tried to launch their own streaming music services in the same fashion as Apple did.

Note that if Apple had required an industry-standard fee for processing iOS subscription payments (generally, 2% or less depending on territory), or didn't require Spotify to use iPay, then there wouldn't have been any antitrust issues.

[musicale]

I think it's interesting that Microsoft got into hot water in 2001 for (among other things) including Internet Explorer in Windows, thereby abusing its dominant position in the OS market to dominate the browser market.

Microsoft very sensibly argued that including (and indeed integrating) a web browser was a logical evolution of the modern operating system.

In 2021, Apple (Safari/iOS/macOS) and Google (Chrome/Android/ChromeOS) would presumably agree with Microsoft's position. Mozilla might take issue.

I wonder what would have happened if Microsoft hadn't been dissuaded (somewhat at least) from completely integrating Windows and IE in the early 2000s. Perhaps Windows would be a lot closer to ChromeOS. And I wonder if Microsoft would have been more competitive with Google, Apple, and other companies if they hadn't been the target of antitrust action.