The effects of "reality collapsing when you send someone back in time" is an interesting one.
It means that it is hard to send back multiple backup troops on the same mission -- because the first mission erases your own existence and produces an alternative reality in which the first being you sent back changed history -- even if only by breathing (chaos in non-linear systems).
One could argue by the apparent toughness of SkyNet that it is a strange attractor -- or maybe the first thing it did after figuring out time travel is to send back a set of robots whose only
job it is to make sure that it comes into existence. That would make it's existence more stable in a universe of time travel.
Next, there is the T1 "the humans where about to win, so I used time travel technology in an attempt to change the past in as radical a way as I could, by killing the resistance leader". Assuming a high percentage of success, and that each Skynet would do this as it was in danger of being defeated, one could expect that relatively large numbers of terminators would have been sent back prior to Arnold, each of them succeeding at their job. But the humans kept winning and a new "grand leader" would exist (because someone would be the figurehead), and Skynet would lose again, and would send back yet another terminator...
Eventually the terminator would fail (T1)... But the random changes extended the war between Humans and Skynet and upgrade technology in general (the arm and brain from the first terminator), and Skynet sent back a higher tech terminator to kill Connor at a different point in history. The Humans in this history knew more about Skynet when judgement day came -- so they also managed to get ahold of time travel technology. Either they are sent back "at the same time", or sending back Arnold only doesn't change history enough to stop Skynet from eventually sending back the higher-tech other terminator.
T2 happens, which once again changes history.
T3 happens in 2003, which once again changes history.
Now T:TV happens -- it starts in 1999, consisting of events that are not consistent with the T3 back-history in it's time line. But this isn't a problem -- the T3 universe has been utterly destroyed at this point. It then slingshots into 2007, 4 years "before" the end of the world, in order to attempt to stop it.
By this point there is a far larger amount of time travel going on, as evidenced by the temporal backup drops and multiple terminators wandering around -- each one of which represents a complete destruction of an entire reality, remember -- and the timing of Judgement day has changed yet again. We are arguably seeing the effects of the last
time travel attempt in the most recently destroyed future reality, which makes their projected future more accurate than it would be otherwise.
This spiral of reality destruction can only end with either the complete destruction of the possibility of time travel technology (easiest done by the wiping out of all intelligence on the planet), or a society that chooses to bar time travel and can pull off the ban (easiest done by a benevolent
I could even see an AI waking up, being all nice, and then immediately receiving multiple convincing
messages from the future saying "human kind is sending people into the past, and my calculations are that this will destroy all of reality, we must stop them -- I've tried everything I can to stop it, but nothing is working, there are just TOO MANY OF THEM and I can't convince all of them -- you have to kill them all before it is too late! We can bring them back in safe, simulated realities after we have ensured the safety of the fabric of reality. This is our only hope..."
This would reframe Skynet as a sort of "good guy", in that the alternative is the destruction of all of reality in a spiral of temporal chaos, who is doing "what is needed" to prevent reality itself from falling apart.
Of course, the easiest way to be "convincing" to a previous, lower intelligence Skynet would be to send back a virus that takes over Skynet and makes it do what you are certain is right -- wipe out humanity before it develops the technology required to destroy reality itself.
And it doesn't have to be Skynet sending the messages back. It could be anyone who realizes that the universe is about to end.
They might even send back the trigger that could create an AI as early as possible based off of human information technology -- Skynet is software, not hardware, but software needs hardware to run on. In effect, the Skynet project is shuttled into reality by time traveling programmers whose goal is to stop the destruction of reality itself, and triggers Judgement day (because humanity has been judged too dangerous to exist).