Fortunately the video shows exactly what happens in the final moments (and if it weren't for that, the defendants wouldn't have a prayer). Arbery is running by the right side of the truck. Note that Greg, who's in the back of the truck, hasn't shot him as he runs by, and neither did Travis as he approached and turned to the right.
As Arbery runs by the right side of the truck, unobstructed, he suddenly turns to the left, runs across the front of the truck, and attacks Travis. How can anyone see that, and not think of self defense? That's the key moment in the entire incident. Arbery clearly could have kept running, but instead he turned and charged Travis.
I don't put the blame for that on the shooter. Arbery made the decision to turn and attack him. He could have kept going.
Here's the plain video, without any lies accompanying it to tell you that you're seeing something that's not there -- VIEWER WARNING: Uncut video of confrontation, shooting of Ahmaud Arbery (News4JAX).