Most of early movies have been lost. Tons of music has been lost. Many old video games are only available illegally. We now have technology to archive and distribute cultural artifacts for little to no cost.
It's ridiculous that cultural preservation has become a legal problem not a technical problem as it was for most of human history.
Trade collapse led to impossibility of making bronze weapons, which further amplified collapse. This was possible because tin mines were few and far apart. So it was a vicious cycle triggered by a weak point, on a background of hardship. The lesson is not to depend on a single failure point.