Tasmanian energy crisis was because of a drought, not because the cable was cut. Tassie exports energy and the power company had lowered the dam levels selling power to Victoria that year expecting regular winter rain. That rain didn't happen. That, then combined with the line fault caused the issue. In fact, the suspected cause of the line issue was that the power company Tassie Hydro zapped the export line with too much current trying to make money from Victoria. That combined with the lowering of dams, perfect storm of greed and bad luck.
In addition, the boats that service these cables are mostly in the northern hemisphere, where most of the undersea cables exist. So there was a ~5 month wait on the repair. I'd expect a 4000Km cable to have it's own fleet of boats for servicing.
When Tassie dams get low, they import power from the mainland. It’s a common seasonal thing. Drought + Basslink outage had the gov buying and running diesel gen at huge cost to keep the grid running. The Basslink outage made a problem a crisis.
In addition, the boats that service these cables are mostly in the northern hemisphere, where most of the undersea cables exist. So there was a ~5 month wait on the repair. I'd expect a 4000Km cable to have it's own fleet of boats for servicing.