It's cyclical. Having one protocol with multiple open clients prevents rapid (if any) innovation, and creates an opportunity for walled gardens to steal the market. And then once the walled garden converges on the local maximum, it creates an opportunity to build a stable open protocol. Which then lasts until someone comes up with the next big innovation that the open standard is too ossified to support.

For all the shit that AOL gets, they basically got the entire country on the Internet. Even the biggest unicorns today have nothing on AOL at its peak.