I found this article difficult to read and confusing.

In the title "... a nuclear strike". In the article: "... not kept in bunkers.. but on regular computers".

Well is the idea to survive nuclear armageddon, or to survive a strike?

A strike can take out a city if that happens the network continues to function - whatever nodes were just lost.

Having everything inside a hardened bunker is not required.

In so far as nuclear armageddon, I am not sure that having computers inside bunkers would help keep the internet up given it requires wiring or wireless infrastructure to communicate.

If Having computer systems still operate, even on their own, then a bunker starts naking sense.