A big drop in hashrate though assumes that you are still in an area that has access to the internet. Of course it might be a doomsday scenario, but in many countries that are using crypto, I imagine the internet is sparse. Sure you could wait it out for a few days or weeks until you get a signal, but nevertheless, you're 100% reliant on something you can't control. So hashrate isn't exactly the worry, but more so access to your BTC and a willing person to accept it. If they know that transacting in BTC might get harder given some major event, they might choose to not accept it.See that's I studied Bitcoin gold BTG, because it does not have a significant hash rate and has been 51% attacked many times. Yet, it is still marching on and it is worth more than $1B. I believe BTC needs far less hash rate than people think. This isn't money, people dont use it for daily transactions (but only to pretent it is money).
Its also its not ground breaking technology, it was in 2009, now its quickly becoming old and stale. Its updates come as often as the Olympic games, its hard to do anything to make it better.
What this is a historical ledger of the first time there was a tech that enabled people to fight back against governments taking people's freedoms away, now the peasants are striking back. In order to secure that ledger it doesnt take much, the fact that BTG is accepted after 50 confirmations and people still trust on it shows that even if Bitcoin were to lose a shiton of hash power, you would still be able to sneak in the Ledger after waiting for a few hours.
I'm not saying a permanent drop of 90% in hash wouldn't lead to a bear market, it would but eventually people start to buy it back up again because even if the market goes to 6 confirmations to 20 needed, it would still be more convienient and easier to hide than gold, it would still have its historical value, etc, etc.
In a way, the higher cost of maintaining Bitcoin is a fee for its premium service vs Gold. In any event, its really hard to drop the hash rate a massive amount in a permanent basis because people will fight back. They can change the hash algorithims to allow people to mine at home, etc. There are a lot of ways people can still make sure their Action Comics #1 is taken care of, they wont let it go easily, its their crown jewel
I imagine that at one point in the future, perhaps paper bills, coins and precious metals might might trade at a premium because of some major hit to the digital infrastructure. Sure it will eventually be fixed, but there could be some crazy few weeks.