ZFS is fantastic and it can indeed restore files that have been encrypted as long as you have an earlier snapshot.
However, it would not have helped in this scenario. In fact, it might have actually made recovery efforts much more difficult.
It could have helped by automatically sending incremental snapshots to a secondary drive, which you could then have restored the original drive from. However, this would have required the foresight to set that up in the first place. This process also would not have been quick; you would need to copy all of the data back just like any other complete drive restoration.
ZFS is fantastic and it can indeed restore files that have been encrypted as long as you have an earlier snapshot.
However, it would not have helped in this scenario. In fact, it might have actually made recovery efforts much more difficult.
It could have helped by automatically sending incremental snapshots to a secondary drive, which you could then have restored the original drive from. However, this would have required the foresight to set that up in the first place. This process also would not have been quick; you would need to copy all of the data back just like any other complete drive restoration.