I think whether it’s theory or not depends on what happens after the US Presidential election. Thought this was a timely share. I don’t think it’s come up in any of the debates so far.
I find the discussion on whether it was capitalism or some other abstract governance model that gave us the Internet to be mostly demagoguery. It's a flashy subject which operates some ultra-broad, poorly if at all defined concepts, lacking any concrete foundations.
I have had the privilege to see Internet (and earlier networks) rise, and happen to know a bit more than an average person about the technological underpinnings of that. So yes, I wholeheartedly agree that it was a big stroke of luck, some very forward-thinking people and the adoption of open standards that contributed to the Net being what it is now. It was also a bit of a lucky coincidence - would ITU be a little less lethargic and invested into its geriatric wired-telephony worldview at the time, it could very well mandate X.25 and related stacks as the foundation of the global net, and everything would be quite different.
But mapping to capitalism or socialism as "the givers of manna" is entirely arbitrary and laughable.
On both sides, mind you. Again, demagogues abound. Mr. Sanders sounds quite noble when suggesting that Internet should be "a public good". Indeed, some countries have already proclaimed and codified that, e.g. Finland (which is very emphatically not a socialist country - see my earlier complaints about people routinely confusing social with socialism). But they did it because they have, to an extensive degree, solved operation problems underlying such a declaration. 5 years ago LTE mobile service in a high-speed train traveling from Helsinki towards Russian border was faster than my home internet connection, and I could buy it for about 8-10 euro (for the sim card plus a weekly package of unlimited access). I am rather convinced that Mr.Sanders hasn't a clue about how to make Internet operate (and most likely, who would operate it, and how that would be paid for, beyond abstract budget assignations (what if budget fails, does Internet stop?))