Haven't you heard fibre optic cables grow in the wild Amazonian rain forests? Farmers harvest them every month and ship them across the world to ISPs needing them.
That's ridiculous. The cables are harvested by independent contractors who wholesale them on auction at regional fairs. They are then binned into lots by middlemen who on sell to exporters, who on-sell to importers who distribute the cables to distributors. The distributors then supply retail B2B to cabling companies who in turn are subcontracted by the ISP's you mentioned.
That is why natural fibre optic cables are so expensive these days.
Growing up in Brazil, I always played with my monkey climbing optic cables trees. Fun times!
Amazonian, I thought we were getting them from that planet where we also mine unobtanium?