Not knowing the situation, it's hard to say..........but, the pilot is usually relying on crew members or a ground spotter to tell him when those guys jump out and when they're on the ground. With the doors on (without the big bubble windows you see on the logging helicopters,) it's damn hard to turn around and look behind you or look down, especially with a helmet on. He had no idea he was pulling those guys through the trees because he probably couldn't see them.
I rely on my medical crew to open the rear doors and look behind and below us, because I sure as hell can't see it when I'm in a vertical drop into a LZ. The NVGs give you even more tunnel vision.
Some of helicopters setup for heavy lift will have a mirror mounted on the front skid for the pilot to see the load, rather than flying blind and taking visual signals from his spotter.