Google owns most people's window to the internet: from the browser and sometimes even the operating system all the way to what sites they get to see, and even the content itself. Amazon handles most online shopping in the US, may have an even larger share in other countries. Meta owns most of the social networking and messaging apps of the world. I'd argue there's plenty of evidence that each is a monopoly in its own category, aggressively eliminating any competition from the market.