It seems important to note, as the article you link does but you do not, that there is no allegation she was trying to steal or damage the cable in use. She was digging for unused cables buried long ago.
That may not be a high-value activity in most contexts, but it is a value-added activity.
You need to consider the externalities of the activity, which in this case includes taking a whole country offline. I strongly believe this would make the whole activity a net negative. I very much doubt that recycling some copper wires produces more value than the cost of losing the Internet and fixing the cable.
Recycling old cables is probably valuable, in isolation, but not when this can occur.
My understanding is that ISPs have good maps of their cables, so I doubt the SPOF was something that didn't know about. However, I take the wider point that calculating all the externalities is at least difficult and probably impossible. At the very least, updating their threat model to include "Grandma with spade" was probably some benefit they gained :-)
It seems important to note, as the article you link does but you do not, that there is no allegation she was trying to steal or damage the cable in use. She was digging for unused cables buried long ago.
That may not be a high-value activity in most contexts, but it is a value-added activity.