Well. The Enterprise seemed to be full of new cadets, except Spock, who was logically in command for much of STXI. Remove Pike, emotionally compromise Spock, and it logically fell to Kirk, who was assigned as XO by Pike.
We also have Kirk's "off the charts" aptitute tests, and so on.
In might not make sense from a strictly military perspective, but it does make perfect sense from a Horatio Hornblower point of view. Still a stretch, but it's not the first (or last) time Kirk's rank does some gymnastics.
Excellent!
I'm glad someone said it!
Roddenberry always pitched Trek as Wagon Train to the Stars and Horatio Hornblower in Space. So this is a wicked comparison to make. I think what happened works well enough considering Kirk is just meant to be a sort of modern take on Horatio.
I said this earlier, and I'll say it again; it makes no sense whatsoever from a Horatio Hornblower point of view, and those claiming it does merely betray their utter lack of familiarity with Hornblower.
Horatio starts off as an ensign, and a rather poor and unconnected one at th at. He has to work hard for every promotion he's given; yes, he advances faster than usual, but he still has to take all the promotion exams, which are quite difficult, and spend at least some time in the various ranks. He is occasionally given command of small craft or landing parties or prize ships, but at the end of that specific mission he is always returned to his original ship, at his original rank. At no point, and despite being just the kind of dashing, brilliant, strategic-minded officer any navy would love to get its hands on, is Horatio promoted simply on the basis of a single, individual action, no matter how heroic, nor is he ever promoted beyond the usual structures of the system, which is to say no ensign-to-commander or lieutenant-to-captain jumps.
The original Kirk was Horatio Hornblower; he was brilliant, he worked hard, he seems to have cultivated good relations with the higher ups, and he climbed the career ladder faster than anyone but without skipping any steps. Abrams' Kirk is Han Solo; he helped someone else save the world (remember, it's Spock who stops the Narada) and they made him a general.
Please don't tell me what I know and don't know. I said I am aware that Kirk is not a literal comparison to Horatio. I know my Hornblower, okay?

As they say on the inrwebs... GAWD/facepalm.


Edit in: You make a fine, very fine point about Han Solo though. Kudos!