How's quantum computer can actually destroy Bitcoin or blockchain lmao? They are vastly two different products. One is a public ledger, and other is technology. Even though, what you are saying makes little sense, but you are referring to a future which is many many decades after of. So, it doesn't matter at all with respect to today. If needed, Bitcoin will also get replaced by something better in future.

Also, aren't you being contradictory when you say that there will be a calamity when all internet and phones and everything will be destroyed, but at the same time land, fiat will remain still? Lmao. When internet, phones and everything gets destroyed, so gets destroyed land, money and even human species.