That's just not true. Nothing ever stopped anybody from starting their own record labels, or choosing their own means of distribution, or opening their own record stores, or any of it.
You're making a common error: You are looking through the prism of the ones who did these things and got successful doing it, and from there you are making the false conclusion that they thus have some magical, preordained hold on the world.
Starting a new label was always pretty expensive. And actually "choosing your own means of distribution" in pre-Internet days, meant dealing with barriers like the total control of radio station playlists by payola from the major labels.