Keeping crypto safe is a matter of concern, since technology is something that can be hacked even though mobile phones and the internet as well. If you download anything from mail as well this could be disastrous. Therefore I do think the only way to make sure that things are safe and your wallet and keys are preserved you have to make sure to :
1. Own your keys
2. Have an offline wallet not online !
3. Have wallets like ledger for more than a certain amount of money and keep it stored in a safe
4. Don't write down your keys on your mobile or upload them anywhere it might be harmful for long term
5. Avoid everything that can get your account or your phone hacked !!
Most of the people investing in crypto are doing it to keep their identity safe and second to keep their money safe. While the data of crypto assets is stored in physical servers, I believe exchanges must be having some kind of safety measures or data back up to prevent losses incase of war or such events. I wonder if there is some kind of crypto insurance in the market
Lloyd's have a new insurance policy for your crypto wallets maybe you can check that out ! But prevention is always better than the cure.