I very much agree that copyright is a tool to protect the wealth of the rich.

But I think the idea of restricting access to knowledge in order to benefit a select few predates capitalism. The ancient Chinese state iron and salt monopoly is the first example that comes to mind, some Greek mystery cults probably count too, even if we don’t think of that knowledge as beneficial now.

I’d guess it’s a common feature of strongly elite-dominated societies, of which capitalism is just the current model.