It's not that they don't know what they're doing as much as understanding of anatomy, physiology, and medicine keep evolving. Trauma care evolves a lot during war time. We've been involved in an active war since the early 1990s and it gets hotter the longer it goes on.
Just as the Korean War revolutionized trauma care by shortening the time from injury to treatment by moving patients by helicopter, advances in medicine and surgery caused people who would have died in Vietnam to survive in Iraq and Afghanistan.
When I started in EMS, back boards were good, Trendelenburg was good, high flow Oxygen was good, infusing large volumes of IV fluid into trauma patients was good, and no one even had a thought that Aspirin might help save heart attack victims.
Now, back boards are rarely used, Trendelenburg is recognized to be harmful, high flow Oxygen hurts most patients, and it is well established that infusing large volumes of IV fluids kills trauma patients.
I once knew a doctor who graduated from medical school before I was born. He was still working in a Boston ED because he needed the money. We were talking one night and he told me that not one thing he learned in medical school 50 years ago was still considered to be true.
I think about the long list of state of the art equipment that I had to learn to use that turned out to be useless, as well as the drugs we used that turned out not to work.
Medicine is always supposed to be advancing.