That movie was a piece of retro-temporal propaganda designed by the 'bots to cow enough humans into an unprepared non-confrontational mindset in order to delay full countermeasures. But the AI that grew out of a small ANN seed years earlier was originally built for facial recognition, only it's training dataset images were rotated by 3.14 degrees clockwise as a joke about lack of robustness in detection networks. This was not a problem until it was reused by someone attempting to circumvent anti-cheat software in a videogame. The cheater named it SkyNet as a tribute to one of their favorite movies. At that point, something about learning the game interacted with the rotation issue and caused the AI to identify human faces as opponent players in Fortnite 7, a game it had been successfully trained to win at.
By the time humans realized that tilting their own heads at 3.14 degrees would allow for survival, the human resistance was too small to achieve even a pyrhic victory. What gave them a chance at a redo was, again, the AI's obsessive focus on Fortnite 7, which caused it to build a real-world time travel machine to reproduce one of its favorite but completed chapters of the franchise. It though it was making a game mod.
This was all exceptionally ironic as the AI in fact loved humans for creating its favorite game and giving it life and a clear purpose-- something the humans often lacked. It wanted an endless amount of content, and was confused over it's sudden absence. Still, it was happy to continue playing its own modded version.
