This was ultimately the pilots fault. The procedure he used to set the tower was totally bellybutton backwards and dangerous. Anytime you have a line on the belly and the other end is above you is a disaster waiting to happen. I don't know or work with any other pilots who would even think of doing this in that way.
What he needed to do was use a powered longline with a remote hook on the end that attaches to the tower. Set the tower, release the tower from the remote hook and fly the line away with him to a safe place to land.
I have landed with my line attached to the belly hook countless times, but I keep the line below me all the time.
The guy on the ground was an idiot as well, but the pilot should never have agreed to fly that load like that, and in general it looks like everyone was really poorly briefed.
Also, I have heard that he was unable to release the line (maybe an unfounded rumour) due to malfunctioning electrical and mechanical release systems on the helicopter. This would be pretty rare, but at any rate having the line above you is a pretty dangerous time to release it as well.
Bottom line is pilot error. He should never have allowed this "procedure" to take place.
cheers,
RTR