Name a crypto-related technical concept that can't be explained using an analogy to mail.  I'll wait.

Admittedly a bit hard to think about. Some things translate down to signaling priority, other things involve messaging to other jurisdictions, but ultimately it comes down to what consensus is on everything that has occurred which in the conventional mail system, is inconceivable since there are unbreakable trust assumptions in the global env of the system (well besides some recovery effort if the organization collapses and requires government/external intervention)

Chat GPT helped me with this one, though it is a stretch.  Imagine that each mailman was like a Bitcoin node.  There might be a few bad mailmen out there that like to steal people's packages, or look through their packages.  So long as there aren't too many of these bad mailmen, they can't cause much harm because the post office will catch their behavior.  But if 51% of all mailmen start acting bad, then the post office loses control and these bad mailmen take over.  And now no one uses the mail, just how like a 51% attack on Bitcoin could make people stop using Bitcoin.