Facebook has a plenty of competition in the social media space, Apple certainly isn't the only hardware manufacturer, Amazon has competition everywhere and so does Netflix. Google hardly runs the only ad network.
> Google has 80% of the search market. Facebook controls 70% of social media.
Wrong way to think about this. If you talk about advertising monopoly, sure. But you'd be hard-pressed to make an argument on a monopoly of free products.
> Netflix put Blockbuster and every other movie rental store out of business.
That's because Blockbuster was, quite frankly, shit. They failed to adapt to the internet. So what? Times move on. Netflix is far far better for consumers.
Something isn't a monopoly just because it's popular.
I wasn't aware Facebook has its own hardware ecosystem or music delivery store, Google does grocery deliveries, and Apple runs its own open import and reseller market.
The "competition" is pretty nominal at this point. The areas of competitive overlap are much smaller than the areas of monopolistic market dominance.