It is just an assumption. I don’t have a huge investment in it.
However, he was the son of the chief naval guy in the Pacific, Admiral McCain. That wouldn’t have made him commander, but it would have had eyes on him among his fellow prisoners.
In prison they were all the same. He was suffering along with them. Why would they look up to him?
Besides being a party animal, McCain distinguished himself as being the 5th from the bototm of his class of over 800 cadets to graduate from the Academy.
Yet, despite that, he got to go the the most selective flight school to become a fighter pilot, which is a shoe-in for fast promotions and top command (carrier) positions in one's career. Personally I don't think a near-flunky would have been so fortunate. I also doubt that he commanded much respect among those who had to work for what they got.