The trucker was at fault according to the following safety video put out by the American Truckers Associations Safety Management Council: https://www.youtube.com/watch?v=TUuykWghNTk

According to the video, the truck driver had a responsibility to secure the right-hand lane to ensure no vehicles were to his right before he initiated the wide right turn. From the video: “To pull wide as you are making the turn, keep your trailer close to the right curb to block the right-hand lane to vehicles behind you.”