There is no reason that someone couldn’t start another Internet.
The reason is that even if they did, it wouldn't be anything worth doing. A network with no domains and no sites other than your own and a couple of friends isn't going to do anything that an amateur radio can't do, for a lot less money and trouble.
You may as well have an electronic tin-can and string.
So while you're right in theory, it's useless in practice.
interesting idea
Your right.
We need to have more than one internet. The more the merrier. It might not be as all encompassing as the one we have now, but it would given time. Big money, big results. Not something some kid that didn’t even finish college could do ...well actually.....