In-law (passed away) was in same class and suite-mate to the Thresher's captain,John Wesley Harvey, at US Naval Academy. They were close friends, and he said he knew the risks. And wish he was alive to learn these details. One thing is certain— the faulty weld in a critical pipe that was for salt water, and thus silver brazed for pressure integrity upon prior examination 14% of the silver brazing was insufficient for pressure applications- a rate that then was determined as “acceptable”. It was later determine by NIS to be deliberate shoddy work in a pattern-(the union violence and deliberate sabotage during construction, a conclusion, but not down to the individuals) but not conclusively singled out as “the” cause. Rather an entire set of design flaws that led to the disaster.
Something to think about- there were 17 civilian contractors—experts in their field, aboard to observe the sea trials— and they were lost with the crew. And, our listening net (no longer top secret) picked up the sound of the failure of an electrical buss that shut down the reactor coolant pumps, causing it to scram— shut down. And from there— no control and the boat could not maintain buoyancy and exceeded crush depth and imploded.