My understanding was that if they rolled back the entire network to just before the hack, lots of transactions would be rolled back that didn't need to be. Tha

My understanding was that if they rolled back the entire network to just before the hack, lots of transactions would be rolled back that didn't need to be. That's why, from what I remember, when etheruem was hardforked created a transaction from the thief's wallet to a new smart contract, and everyone agreed to validate that transaction even though it wasn't signed by a private key.