[conartist6]

What will happen instead is standards, because the fragmentation of these monopolies would instead leave people unable to communicate with each other.

People want to be able to communicate with each other! For example because people want to be able to communicate with each other, the EU made it law that messenger apps must embrace competitive compatibility.

Once you have standards a clone of a UI or even a backend is no more threat. People can customize clients and servers to no end at that point -- they can do anything but break the shared expectations.