A common complaint with Star Trek from longtime fans is “where are the time police?” - those people from Voyager and Enterprise whose job it was to make sure nobody messed up the timeline.
Here’s my answer:
Crewman Daniels from the 31st century time police (seen in Enterprise) didn’t stop Nero’s mission because Daniels and his time police are from the post-Star Trek XI timeline! Go back and check – he never made a single mention of specific TNG, DS9 or VOY characters or events. From Daniels’ perspective, Nero’s incursion into the past is part of the normal chain of events.
The reason that Captain Braxton’s 29th century time police (seen in Voyager) didn’t get involved is because they were erased from the timeline by Nero’s actions. Ever wonder why the 29th century guys never got involved in the 22nd century time war but the 31st century guys did? It’s because from Daniels’ 31st century perspective (and that of the entire temporal cold war) they never existed. They’re from the same timeline as Voyager (and TNG and DS9), which ceased to exist (at least in its current form) when Nero blew up the Kelvin and later imploded Vulcan.
Problems with this theory: The 29th century Timeship Relativity is said to be “protected from changed in the timeline” presumably by similar shielding to what Voyager came up with in VOY: ‘Year of Hell’. Maybe their shields were down at the time? Or they weren’t powerful enough to survive such a big change? Maybe the ship survived but the crew didn’t, which is why 31st century Daniels’ wears that stupid looking Time Suit.
Also I’m assuming one timeline, contrary to Bob Orci’s many worlds theory. The film itself leaves it up to the viewer (alternate as well as or alternate instead of?)
:during the mind meld there is a scene of Tovok where he was helping Spock with the red matter as a Vulcan scientist but I am probably wrong...