Re: Why didn't Chekov ever make Captain?
Likewise, Admiral Kirk wouldn't have lost his credibility by posing as the skipper of the Enterprise...
I don't know. Part of what I found so annoying about Kirk's character in the films is that he kept doing exactly that no matter the situation. It was a relief when he was finally demoted back to captain so we wouldn't have to wonder whose toes he'd step on next to get the Enterprise
back. Fortunately, Stephen Collins has more of a sense of humor about it than his fictional alter-ego did.
"Many things seem clever to an imbecile." --Captain Thelin th'Valrass, USS Enterprise-- "The Chimes at Midnight"