He either stood up, or placed this tower in to position. then for some reason (i assume because many hooks require a bit of weight on the hook to release) was forced to descend next to the tower. He very likely asked the guy on the ground to give it a tug because it wouldn't release without any weight.
I would have used a remote hook or a grapple hook, or if he was just standing it up, hook two lines together. Don't ever descend next to your line.