And that's why it's great that the internet exists. A very large number of libraries can burn and no knowledge will be lost. Just copies of that knowledge.
Those Alexandrians' should have focused more on their tech game. :)
Alexandria wasn't the only library in its day, obviously.
Sometimes you "only" lose redundancy. But occasionally a lost library (or digital archive) contains unique content, so statistically the survival rate still trends toward zero.
How is knowledge lost? "Slowly at first, then all at once."
What will happen to that digital knowledge if there is no electricity in the world for like… twenty years? I am not even thinking about “twenty generations”.
Those Alexandrians' should have focused more on their tech game. :)