From what I could gather from the video was they were at a Shell station and there was a big traffic jam of mostly Power Tour participants on the road the gas station was on. with cops directing traffic at a light or stop sign down the road.
There must have been a delay between when the truck driver waved and the time the line of cars started moving after the cops started directing the traffic through the intersection, and the vehicles backed up were accelerating. They started to pull out, the truck had started to get some momentum going, and "boom".
I know from experience (and I have many decades of it living in the suburbs of Chicago with the congested roads here) that even if it looks like someone is going to let me in from pulling into a line of traffic from a side street or parking lot, to keep my head on a swivel, I look right for the cars to start moving, and as the "domino effect" approaches the car in front of me and I know it are about to start moving, I look to my left to make sure the car or truck I thought was going to let me in is really going to let me in! You have to keep your head on a swivel or else you will get hit someday.
Sometimes you have to be aggressive to butt in or else risk sitting there forever, but still you nudge forward trying to force the driver in the line to your left to make space, and if they decide to be an a-hole that doesn't want to let you in, "gotta know when to fold em" and not push it.
Whatever the case it sucks about the Hornet, I worry more every year when I take my vintage rides out that I'm going to get run into. I am always cautious but put my defensive driving techniques into overdrive when in a old ride! I realized after I bought my Magnum last year, if it ever gets tagged, I don't know if it would even be possible to find the parts to repair it!