[yanmaani]

> wouldn't gaining access to everyone's wallets render it useless since BTC would no longer have value

It would only be useful for the wallets with known public keys. That's mainly old bitcoins, new ones only have its hash written to the chain.

This would certainly crash the price, but not to zero.

> Also, wouldn't we be able to restore everyone's wallets from the latest snapshot on a new blockchain?

Yes, but what good will it do you if the private key is leaked?