I saw that last night. Civic driver shouldn't have overtaken, but truck driver is not completely fault free.
Look at the distances, his speedo and the cars ahead. He is "gaining under braking" on the two cars ahead of him as they come up to the speed signs, and then doesn't brake until near the point of impact. He should have been reducing his speed as he saw the brake lights on the cars in front. It was either deliberate, or he was too concerned watching the civic in his mirror and getting ready to beep at him. The gap was closed and he squeezed the civic and then punted him.
If you listen to the audio he tells the civic driver something along the lines of he's done it to him before or tried doing it before.