MJPollard said:
Theory:

Based on all of the information gleaned so far, we already know that Nero went back in time (as explained in the "Countdown" comic) and wiped out the USS Kelvin, an event which altered the timeline. Not drastically, but enough. When Starfleet finds out about the Kelvin, they assume that they're facing a Really Big Bad (I'm pretty confident that Nero lays low for now) and go on a technology upgrade tear to fact this new threat. Hence, the alternate USS Enterprise looking a lot more technically sophisticated than the prime USS Enterprise.

How does one changed event affects so much to the point all the characters are different?

the Wipe out of the USS Kelvin is one event which affects Kirk's life, but how are Bones, Spock, Sulu, The Enterprise and so on affected too.

Why do I feel that this movie will not go into those details.

a technology upgrade tear to fact this new threat

Yeah, but upgrading the technology to 24th cen. like technology is too far.

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