It's a new timeline created by Nero's interference. Anything could happen.
Indeed... including breaking with the tradition of clear character motivations and believable plots and instead offering an action thrillride with "plotholes of fortunate convenience" galore.
The problem of the movie isn't that it creates a new timeline... it's that it constantly requires the viewer to make huge leaps of faith within the new timeline.
It really got out of hand in the 2nd half of the movie ... the first half was actually quite good... so i guess you could indeed say they got it "half right" LOL.
After this movie the real question won't be whether Trek Fans may also be BSG fans, but whether Trek fans can still be Trek fans.
So Kirk got stranded on a barren ice-planet... , despite it being just a wee bit untypical for Spock or any Starfleet officer to make such a decision, even when emotionally distressed, it was quite fortunate really, because it allowed the producers to re-use some clone of their previous cloverfield movie monster to chase Kirk around to the ohs and ahs of the audience. So now Kirk is stuck on an ice Planet? Well yes... but fortunately , out of all the places he could have landed, he landed within walking distance of the one cave that future "old Spock" choose as his living quarters as he was abandoned on the same planet. Yah well, so now Spock and Kirk are stuck on the same planet right ? Well yes... but fortunately there is also a Federation outpost within walking distance, which is fortunately crewed by Scotty, who in the future was fortunately able to figure out how to beam people across interstellar distances, which is really fortunate, because fortunately Spock brought Scotty's formula from the future so they can beam themselves back to the Enterprise which is currently in warp. Fortunately this technology will propably be forgotten if there ever is another movie because otherwise the Federation would have a tactical and strategic advantage that would allow them to quickly take over the whole universe with little resistance.
Know what i mean ?

It has nothing to do with the timeline switch... it is simply a very very very badly constructed plot that has holes in it all over.
It's constructed like a 5 year olds ramblings, but nothing you could call a "well made plot" with a straight face.
As someone else aptly put it: It's like they had some kinda committee that got told what was gonna happen next and then had to come up with whatever bull***** reason they could think of to make it happen.
Aright! So next.. we need Kirk to fight a monster! That will be cool right!?
Yeah well, but he s on a ship!
Ok we got to get Kirk off the Ship!
Lets have Spock space him!
Woha cool! Lets do it!!
Wait, how does he get back to the ship?
Well he can totally meet Spock there ! From the future! and Scotty will beam him back!
Wait, Scotty is there too ?
Well of course! How else are they gonna get beamed back to the ship ?
WARGGRAHGRAGRL ??????