^That's kinda how I was going to put it.
This reminds me of a bit in a (non-sci-fi) book I read recently. (It was one of the Robin Hudson mysteries by Sparkle Hayter, The Last Manly Man,
I think.) In it, she says that time travel must be impossible, otherwise murderers of the future would realize that the past is a pretty good dumping ground for dead bodies and we would keep seeing all of these anachronistic corpses showing up. Not to mention, if timetravel were possible, why hasn't someone killed Hitler already?
One of the things that makes The Terminator
relatively unique is that it's a time travel story told from the perspective of observers in the past and not the travelers from the future.
If we accept the inevitability of the existence of time travel, then it follows that the past would see the effects of future events. SOMEONE always traveled back in time. This individual then did things that helped to form the past & future that he already recognized. The present only happens once.
Take a step back and look at events from the linear perspective of time.
1.) On Thursday, May 12, 1984, Kyle Reese suddenly blinks into existence, seemingly from nothing.
2.) Kyle Reese impregnates Sarah Connor, then dies.
3.) John Connor is born.
4.) Skynet declares nuclear war on all humanity. Judgment Day.
5.) Kyle Reese is born.
6.) In 2029, Skynet invents a time machine.
7.) John Connor's human resistance takes control of the time machine. Kyle Reese suddenly blinks out of existence.
This is all that ever happened. None of these events are changable. The universe doesn't care why Kyle Reese suddenly blinked into existence in 1984, he just did. The fact that this would ultimately create the circumstances that would lead to his getting sent back in time in the first place were inevitable.
And here's another thing to consider. Why, of all dates, did Skynet choose May 12, 1984 to try to kill Sarah Connor? Why not try to kill John Connor at a later date, when it's less likely that their Terminator will cause collateral damage to the timeline that might endanger Skynet's own existence? It's because May 12, 1984 was the last date where Skynet could be reasonably sure of Sarah Connor's whereabouts. Why? Because that was the date that the T-800 started hunting her and forced her into hiding. Unbeknownst to Skynet, they were already constricted by their own mess.