Even if you have the perfect backup system, unless someone else understands it and cares as much as you do - well.
Goodbye, secret files When I'm gone, all this information will die
Some things we know because they are carved out of stone
Some things we know because they are built at monumental scale
Some things are saved by the vagaries of fate. Fossilized, drowned in a bog, or carbonized in just the right way to nerd snipe a generation.
Some things we think we remember from antiquity, but really they only ever existed for a small class of Americans in the 60s2
But what actually works consistently, and with intention? The most human method of preservation - which is replication.
Rhapsodes read the odyssey aloud, Peisistratos demands a written copy be created, Alexandrian scholars copied and annotated. Through countless purges, rebellions, wars, new copies were were created, secreted across borders. Then the printing press created so many copies that posterity was guaranteed.
The Ise Grand Shrine is rebuilt every twenty years, ensuring that is in constant good repair, and that the knowledge of how to build such a structure is maintained.
The members of r/DataHoarder download US government data on pricing and climate, distributing it amongst hundreds of peers via bit-torrent - because they believe that truth should be preserved.
1 M-discs claim to last for up to 1000 years when stored in an ideal environment. Hard to test this though. And you better hope whatever format you store your data in is still supported
2 This one goes out to all the trad spouses in the audience