Remember that they're replacing seabed fibre that was damaged by the eruption - news reports this week say that they went to fish it up this week and couldn't find it (around the point of one of the breaks) - I'm guessing that TDR measurements from both ends give them numbers that don't add up so they know there are at least 2 breaks.

That fibre is a dogleg from Fiji to Tonga - and will get repaired relatively quickly so I'm not sure about "outlives" - certainly there will be people in Tonga who may choose to continue with starlink but it may prove to be too expensive for most people (one the other hand the govt may choose it for some outlying islands)