There are exceptions to the notion that competition is good. If we attempt to map out all the exceptions, we will be left with mumbo jumbo. Economic libertarianism is the true death of the brain. Some monopolies are good and any threat to the monopoly is a threat to the consumer.
More than that. They own the content and relationships and can use them in ways you cannot predict. LLMs gobble up human produced content because we entrusted it to corporations. What hit hardest for me was when Facebook published a study where they found they could influence users attitude by prioritizing certain posts in their feeds.
Imagine it. Corporations owning your relationships and using them to get a profit out of you