Almost every currency is volatile, including the Fiat currency. Traders are taking profit from the Fiat currency like "lnstaforex". At least 5-10 years' time must need Fiat currency to twice dump or up. Crypto is a very highly volatile market compared to Fiat currency. Although world war or war effects we will see in both USDT and crypto. We can't be safe in any currencies, but gold has a real stable price even after any war.
Fiat was less volatile rather than crypto since it was controlled by centralized entity so i suppose it's impossible to replace fiat and i was really agree with you, Some crisis can have some significant impact to the economy including fiat but i think it's will having small impact on the crypto expect global crisis as you said but peopel see crypto as digital gold so it's good as an store-of-value beside gold.