The internet was designed so that any machine can reach any other. That still holds, and for anything of a serious size it turned out not to be good enough, which is why a large industry now exists to make sure you almost never talk to the machine you think you are talking to.
The constraint is not bandwidth. It is distance, and distance is the one thing nobody can engineer around.
Light in a fibre covers about two hundred thousand kilometres a second. A request from London to a server in California and back travels roughly twenty thousand kilometres, which costs a hundred milliseconds before anything is processed, before any equipment adds delay, and before the first byte of anything useful moves. A modern page makes dozens of these round trips, and they largely happen in sequence because each one tells the browser what to fetch next.
No amount of capacity fixes that. You cannot buy your way past the speed of light, so the only remaining move is to stop making the journey.
Which is what these networks do. They put copies of popular material in hundreds of locations and answer from whichever is nearest, so the request that appears to cross an ocean actually terminates in a rack twenty miles away. The logical map still says one server. The physical map says thousands of caches, and the physical map is what determines whether the page feels quick.
Video is what turned this from an optimisation into a requirement. A page can survive being slow. A video that stops to buffer is a video nobody watches, and serving a popular clip to a global audience from a single location is not difficult so much as arithmetically impossible.
The part I find worth sitting with is what it does to who can publish.
Putting something on the web costs nearly nothing and always has. Putting something on the web that a million people can watch at once requires a contract with a company operating machines in eighty countries, and that is a capital expense with a floor well above what an individual spends.
So the protocol remains open and the economics quietly sort publishers into those who can afford reach and those who can only afford presence. Nobody legislated that and no rule was changed. It falls out of geography.