Agree about always walking towards incoming traffic side so you can see cars, but I don't think it would have really mattered as much in this case because that does look like the driver intentionally ran them over.

The fact that it was so smooth is the reason it looks intentional. Since the people were walking with their backs facing traffic, the driver could line up well in advance where as if the people were facing traffic, then the driver would probably have to jerk over at the last second to hit them intentionally so that the walkers wouldn't suspect it before hand.

The driver never slowed down or reacted in a way that would suggest they were surprised that they went off the road and hit something, the driver kept on going and smoothly exited the area without slowing down the slightest (might even look like the driver sped up).

I think anyone that had unintentionally gone off road and hit something hard (and assuming they weren't exactly sure what they hit but had a hint it was one ore more people) would brake hard and or make more erratic maneuvers (e.g., turn the wheel hard to get back onto the road and probably brake at the same time). Obviously that's not going to be the case all the time, but I would bet that's how the majority would react.

Seeing other unintentional hit and run videos, the drivers almost always perform some sort of maneuver that suggests they were surprised by what they just hit as well as braking, the driver would slow down enough to process the event, then make the decision to run, which is indicated by the sudden increase of speed after enough time had passed since the hit for the driver to process what just happened. This is as opposed to what an intentional hit and run would be: hit and run at the same time, not stopping, not slowing down, not making sudden surprised maneuvers, etc.