Additionally, a lot of people don't realize its not on only the main company the ship is attached to. Multiple vendors come together to make a single gear, coupling, etc. It got to get carved, heat treated, coated, etc. It's a ton of legos that go into making a complex piece of machinery. Then a bunch of those complex pieces of machinery making one major part of the ship combined with other complex pieces.
A lot of companies are going to be looked at and the mistake could have been from any of them.
For example, with airplanes it's not just Boeing. You have to look at their suppliers. Then their suppliers got to look at who make the parts. Then those people got to look at who was involved with the processes of those parts. It's not like Boeing produces and manufactures every single thing in their hangar.
Boeing's main job as an airplane maker is to be a master in getting all the parts in the right place at the right time. '“We can’t be experts in everything," one executive says.
www.nbcnews.com
If 99/100 companies do their job, all it takes is one company to screw up. I remember this warehouse I used to work for produced one part for an Air Force fighter jet (F-15 I think) and they had to ground an entire fleet/squadron because some vendor we hired (and are very reliable) screwed up and it went up the chain without anybody double checking all the specs. It went live right onto jets that were considered active/ready and had to be recalled. Someone said they found the president wasted and drunk af late in the office after getting the news it traced back.
This is why we need more engineers and less finance people pushing/rushing them.