Maybe you need to remember that 'history is written by the winner'...
and to realize that we are being told a progressive story, told over the years, as more chapters are fleshed out, by different thinkers, different writers, producers, directors and actors...
At the end of each Terminator movie, we hear a voice from the future, giving us hope for that future, a future when the machines don't dominate and destroy humans... so, at the end of each movie, we know that humans win, because they survive the past to be the voice of the future... but, because of the nature of time-travel and the whole history being written by the winners thing, we also should know at the beginnings of the movies that humans win, or who would be there telling the story from the future??
or, imagine you are watching the story 'as it happens'... only watching as the new wrinkles in the space-time continuum occur, only watching 1 new branch of future history of things to come play itself out.. people would be too confused if there were 'other' T2s or T3s or alternate versions of that history, but those alternate histories are possible, if you believe they are possible... read the fan-fics or novels to see the way things 'could' go... whatever you want to believe, is 'true' since the whole Terminator universe is just a work of fantastic-fiction any way..
also consider, SkyNet doesn't know the T1 Terminator will fail, until 2029, or 2032, or whenever the humans DO finally win (or win again...), so at first, humans win all on their own, led by John Connor the great military leader with 'no past'... which inspires SkyNet to send back a Terminator to kill John... T1 (T-800) fails, so SkyNet sends back T2 (T-1000) to try again at some future date when John is more vulnerable, his mom is gone, John is unprotected... T2 fails, and the humans do win, take over the TDE and send back their forces to help themselves win, by saving John in the past... The machines still fight back, reclaiming or rebuilding the TDE elsewhere, T3 happens, and the Machines rise... before the humans finally figure how to beat the machines completely...
we have yet to see how the humans manage to rise above and finally defeat the ever-present machine/computer presence in the future of things to come... we don't know the final ultimate twist, there's a chapter or 2 left untold at this point...
but, in the end, we do know that the history is written by the winners, so we already know that humans win in the end, when ever the end should come... SkyNet's mission changes in T3 too, from killing John, to killing lieutenants of Johns, to make it that much harder for John to rally the humans to victory... in the original history of things to come, SkyNet came to learn that the Anderson bro and sis, and Jose Barera, and 20 others, including Kate Brewster and her father, were lieutenants, or integral connection to John and the human resistance...
what affect on the future of things to come will TX killing Jose Barera, the Andersons, and General Brewster have?? we won't know, until the real T4 happens... all we do know now is that Judgment Day was inevitable, because if Judgment Day and the war didn't happen, then T1 and T2 couldn't have happened any way... right??
now we just have to wait and see how it all comes together, and what happens after the history of things to come is all played out...
and, as far as John and the resistance destroying whatever central core SkyNet is or will become, we only have the end of T3 left to confuse us, when John thinks its all over, before he knows that the future, and his destiny as that great military leader, are still only on track to be played out... SkyNet only appears to be as a virus, because of the way it infected everything so that it could be activated and released to take over everything... SkyNet probably still has a 'central core' or a few central locations which, once destroyed, will free the machines from the central computer control, and allow humans and machines to once again live together, in peace, rather than to always fight to destroy each other...
we'll have to wait and see... at least until my T5 is finished and posted!
