I worked on pipelines for part of my career in maintenance planning, not in construction. I’ve been trying to guess at how a rescue operation could have been attempted in this case. I’m not aware of any mechanism for cutting into the pipe at the depth the divers were stuck that wouldn’t immediately result in flooding the pipe, or risk cutting through the divers. The only rescue option that I could guess at is divers going in from the end of the pipe, swimming down through the length of it, and somehow pulling the trapped divers out.

Maybe the owner/state should have let rescuers give it a try, but that rescue option sounds terrifying as hell.