Huge differences in towing behavior between the full scale plane and model. The full scale went to low level minimum flying speed flight to give sailplanes the opportunity to get in line and fly straight. Only when order was established and verified did he climb at all.
The model towplane pilot firewalled the sucker and immediately assumed high angle climb status, before all sailplane pilots had their trim straightened out and were in-line, in control. He was a large cause of the fiasco that followed. Note that all the sailplanes did not crash. Perhaps four of them did, a fine showing for such a terrible tow job.