Basically, it involves a larger corporation creating a thing that hooks into an open standard, artificially inflating it, slowly adding new, proprietary closed-source features that other members of the open standard cannot use
While I wish ActivityPub was GPLv3, it is at least under the MPL, and they are going to have a hard time introducing proprietary closed-source features on a communication platform that requires them to share the source code.
Twitch is overly hostile with its own subscriber base and doesn't pay nearly as much as YouTube. {Recent business decisions](https://digiday.com/marketing/how-twitch-lost-its-grip-on-and-way-with-the-streaming-community/) are really causing it to bleed streamers to other platforms, mostly YouTube.