This is something that keeps me worried at night. Unlike other historical artefacts like pottery, vellum writing, or stone tablets, information on the Internet can just blink into nonexistence when the server hosting it goes offline. This makes it difficult for future anthropologists who want to study our history and document the different Internet epochs. For my part, I always try to send any news article I see to an archival site (like archive.ph) to help collectively preserve our present so it can still be seen by others in the future.
I believe this is a fallacy. Things get preserved haphazardly or randomly, and “importance” is relative anyway.
In addition, who decides “importance”? Currently importance seems very tied to profitability, and knowledge is often not profitable.
It is relative, but it only takes one chain of transmission.
AskHistorians on Reddit had an answer about this. Stuff is flimsy but also really easy and cheap to make copies of now.