It sounds like they had a really bad backup system for this to happen.
No one will ever trust them with their data and email again, so they might as well close their doors straight away. It’s unfortunate but a mistake like this is likely gonna cost you your business.
It's not offsite backups that would have saved them, it's offline backups.
You can have all the data centers you want, but if they're all connected, then one ransomware attack can (and did) nuke them all.
If you have just one system that's unplugged with a copy of all the data, then your data will be fine. It's just time at that point, which could still be very very bad, but the data still exists.
*Danish hosting firms CloudNordic and AzeroCloud have suffered ransomware attacks.
During a data center migration, those servers were connected to the broader network, allowing the attackers to access critical administrative systems, all data storage silos, and all backup systems.
Danish media reports that the attacks have impacted "several hundred Danish companies" who lost everything they stored in the cloud, including websites, email inboxes, documents, etc.*