All you autists bitching about him failing to brake or take evasive action have failed to consider a couple of key factors.
1) dashcams have fisheye lenses that distort distance and angles. This is so that they can capture the maximum width of surroundings. So what may appear to you in the video to be a lot of room might actually be closer to half that much room if viewed with your own eyes IRL without the lens angle distortion. Everything looks easily avoidable in dashcam videos.
2) If you have much experience with driving, laws, and insurance OR if you read the stories of others that do, you will realize that it is not always to your advantage to try and take evasive action to avoid a wreck. Sometimes your attempt to avoid the wreck on one side can cause a wreck elsewhere, either because you lose control or you are forced to hit something else. Or sometimes another nearby vehicle then has to take evasive action and overreacts or underreacts and that vehicle causes a wreck, which may or may not involve you or be worse for you than the one you originally tried to avoid. And guess what? If someone runs you off the road and you wind up losing control or hitting something else as a result, the first vehicle gets to drive on with zero consequences or liability, and now YOU are liable for 100% of the incident, because no one contacted you. Even if you do try to avoid it and slow down just enough that they barely make contact, they can just drive away and again they are likely not to get caught and you will be left with all of the liability.
Go on youtube and watch some dashcam compilations...you will probably run across several that demonstrate this. A few months back there was a good one that showed this clearly. A minivan passes a cammer illegally and brake checks him hard while still merging in front of him, cammer brakes hard and tries to evade to the right to avoid, winds up losing control and fishtailing off the road, van continues on his merry way, cammer takes 100% of the loss because the van technically didn't touch him. If the cammer had held his place the van would have sideswiped him and either wrecked himself or at the very least probably have had to stop and take some or all responsibility for causing it. There is another where an SUV does something similar to a semi driver and eventually the SUV pits herself on the front of the semi and is found completely at fault due to the semi cammer's footage.
But yeah, sure, let's just let OT be OT and pile on with more of the "dur dur wHy DiDnT yOu BrAkE!!!" and "you could have avoided that so easily!" comments.