This seems really poorly designed and planned. First thing that would have helped would be to make it mandatory, so you could plan to have people from each discipline present, and plan a challenge based around the people available.

First, only 4 out of 13 team members joined, that's a huge difference in manpower. Second, a bunch of the failures he listed point directly to a lack of product/project leadership - because those people noped out. Finally, as dumb as this sounds, you can't team build with 3/4 of your team not participating...