The man most directly responsible is Miles Bennet Dyson

“You are what you do when it counts.”

- John Steakely

Of all of the character arcs within the film, Dyson goes through the most tumultuous change of all - not only from an internal standpoint, but also in the eyes of surrounding characters and the audience.

This begins in the moments following the attempt on his life. As the T800 lays out the entire sequence of events, notice the way Dyson is presented – the scene is reminiscent of a police interrogation – the gliding & rotating camera angle, the positioning of John, Sarah and the T800 as interrogators, Dyson’s wife in the lawyer position, and Dyson himself, staring at the ground as if guilty of a crime.

A key point is Dyson’s response to the nature of proceedings.

Miles Dyson: “You’re judging me on things I haven’t even done yet. How were we supposed to know?”

The Dyson seen here is not the person that exists in Sarah’s mind. Instead, we see a family man with the intention of bettering humanity. This strengthens the point of separate iterations on one timeline – the Dyson of the future may well be different, but this current iteration is not the man that will cause 4 billion deaths. This is further heightened with the visual symbolism of the road at night, the process of travelling analogous to the process of becoming – at once both long in the journey and sudden in arrival at the destination. This can be seen in Dyson ’s character arc – a literal long journey for Sarah to meet him and a sudden arrival at his heroic final iteration – it is solely through his sacrifice that Sarah and co. are able to break the timeline that leads to Skynet’s development.

As a final point on this topic of becoming, a curious detail underlines the Cyberdyne iteration of Sarah. During the lobby entrance scene, notice that she is wearing the same coat as Reese in T1.

How this coat is obtained is never brought up. it’s clearly not from Enrique, as he lives in the desert; so the alternative is that it belongs to Dyson. However, this is also unlikely due to the climate. Therefore, the most likely explanation is that of intentional symbolism. It serves as a visual representation that this Sarah has overwritten her earlier iterations:

From vulnerable teenager, to manic doomsday prepper, then to pseudo Terminator, and finally to the Kyle Reese noble protector role.

Though Sarah’s self confrontation is a milestone in realization, it’s in the finale that we see her ultimate identity manifest.