The proof of Kirk's capacity to command is that he proved not to be the clueless patsy Marcus was expecting him to be.
The writers hedged the bets there a bit, having McCoy complain about how Kirk isn't well and should be resting. Kirk wasn't just an angry young man, he was an angry young man who had banged his head badly, judging by McCoy's constant tricorder-tickling. Perhaps he got better en route from Earth to Qo'noS?
One wonders what other hothead Marcus could have had in mind. Also, it seems the
Enterprise was already a major element in the plan: it would take time to arrange for the warp core sabotage, and the torpedo chutes might have been custom jobs, too, requiring even more lead time. Planting a suitably vegetative captain into the center pot of the
Enterprise should also take some effort, so it really appears Marcus was acing on a long-term plan where Kirk commanding that ship was a setup from the get-go.
Who knows, perhaps Marcus also arranged for Kirk to be poisoned somehow for the mission? Perhaps he had spare Ceti Eels and slipped one in during the penthouse massacre? This would give him more leeway with the choice of the patsy...
...Although I still feel Kirk is such an unlikely
Enterprise commander that this must have been a two-step plot where Marcus uses the unwitting Pike to get Kirk to do the dirty work. Which brings attention to the fact that Khan is a fantastic marksman, even with heavy weaponry. It should have been easy for him to selectively assassinate Pike and leave Kirk alive in the massacre, to effect the exact outcome that Marcus desired for his plot of sending the long range torpedoes to Klingon space. Lots of coincidences and implausibilities eliminated there:
- Getting those torps to the KNZ really, really requires Khan and Marcus to cooperate, up to a point. And of course they would, as Marcus is Khan's boss and Khan is his clever advisor. After that point, their respective betrayals of the other party would come into play, but until then, they would trust each other (that is, trust that the other is flying into the trap arranged by the other).
- Having Kirk command the
Enterprise must be the result of incompetence or malice. Okay, so here it's malice!
- The mechanics of that malice are pretty clear, too: Kirk does what Pike says, and Pike does what Marcus says, for the exact same reasons. And carefully killing Pike is a very precise and reliable way of preparing Kirk for the job at hand.
Okay, enough coffee for today. But both the movies do appear to contain the rationales for the seemingly irrational bits: this is not how Starfleet normally works, but it is how the Starfleet we know could work in a crisis of this exact description.
Timo Saloniemi