How would a country’s tax department not have a backup system that can handle this? Surely they would know they are a prime target, and so have air-gapped backups in addition to an automated backup process?
Valid question. But on the other hand, Russia doesn’t seem like they are well organized in anything they do. And normally they’re the ones hacking the rest of the world, they probably didn’t expect to be on the receiving end.
I’m wondering how Ukraine know they got all the backups. Maybe they only got one or two levels of backup?
The attack also reportedly resulted in the complete deletion of configuration files crucial for the functionality of Russia’s extensive taxation system, wiping out both the main database and its backup copies
Maybe they think they’ve deleted all copies of a decryption key?
The chaos itself is worth a lot, but beyond that, the thing you have to understand in regimes like Russia is the massive incentive to never admit any kind of failure, which results in an increasing build-up of little lies as you move up the chain of command so that the dictator's close circle can tell him that everything is wonderful, when on the ground it's a disaster of people terrified to admit any kind of fault.