A sufficiently powerful company or group could promote a third party app store by negotiating exclusive deals. Imagine a "EpicTwitBook" store being the only way to get Instagram, Snapchat, Twitter and Fortnite.

Previously those apps were forced to make concessions to be on the iOS store, and I could download "Instagram, the version that makes Apple happy" app.

But now, that version of the app is gone! I google "Why is my Instagram gone" and get an article that says I have to sign up to the "EpicTwitBook" store, and download the "Instagram, the version that makes Advertisers happy" app.

I would prefer the first version but I don't get a choice.