- it's a specialized business requiring specialized ships which are often booked out a long time in advance
- the damage is in a war zone
Would you be willing to do your job in a war zone? Would your boss be okay with sending you there? With sending very specialized and expensive equipment there with you?
Also what do you think would be sufficient to provide peace time equivalent safety guarantees for the ship and crew? Military equipment and crew ain't cheap either.
They're actually not booked out a long time in advance. Usually in case of a fiber cut on a major subsea cable, the crews will be out to fix it within a couple days at max.
The real issue is the second fact you identified, that it's cut in middle of a warzone. I don't think they will risk sending a ship out unless closely escorted by military vessels.
Welding undersea fiber under fire isn't in any of the technicians' job description, so while they say that everybody has a price, it's possible that the bid-ask is wide enough that you could park an Ever Given sideways there and there'd still be room. These folks probably make enough already.
So then it’s possible a US military option (involving the Army Corp of Engineers) will be required to fix it. Those soldiers have experience doing work in the line of fire and have no ability to refuse.