I was told by my nephew, who also spent quite some time up in nam flying 210s that most of the guys there are guys that (like himself) could not get into other companies, for whatever reason. usually extremely low time chaps, and not always the sharpest tools in the shed.
This by his own admittance, as one such pilot, who just scraped through. Obviously after a few thousand hours he is now flying for a domestic carrier, and has caught up, but he says that is the weakness of the nam crews.