The internet is vulnerable in a few ways. From an infrastructure POV the internet is mainly undersea cables and there actually aren’t that many of them. Or, we are reliant on surprisingly few of them. Only about 400 in total and a handful of main ones I think. They were owned and operated by telecommunications companies, now google and Facebook etc have muscled in, and where they come into land is closely guarded. If these were cut sections of the worlds internet would be gone, especially more isolated regions of the world. And the rise of private ownership of the cables is a vulnerability in itself too.