It is interesting to see no games were developed using C, C++ or Java and outside of JS for web games it is all C# and Unity.

I don't really follow game dev, is C# popular in the industry then? I know a couple of popular indie games were developed using C# and Unity but has it made its way into the bigger studios?

I'm guessing that the time-crunch of being a "game jam" drove most of the participant's decisions to use Unity and C#.