Seems like a prototypical diversity problem: the bros at github that designed the challenge couldn't find anyone in the room to whom the challenge wasn't obvious, easy and brilliant. :-)
This is exactly the sort of problem increased workplace diversity helps to solve, and it's a great argument for an expansive definition of diversity, which includes traditional measures such as race and gender, but also non-traditional measures, such as socioeconomic background, education, etc. (To wit: The best engineering team I've ever worked on was three computer science grads, two boot-camp grads with backgrounds in chemistry and sports medicine, respectively, and myself, with a degree in English lit but extensive industry experience. We all brought different things to the table, and we produced robust, maintainable services.)
This anecdote doesn’t surprise me, there was a study done some years ago that looked at paper citations and there was a strong correlation with diversity of the team and citations. What I remember of the excerpt was that they didn’t just look at common things like gender and skin tone, but also tried to take into account class and economic diversity as well.
I didn’t scrutinize the paper as much as I probably should have, but it definitely fit with my personal experience that diverse teams tend to be better. (yay confirmation bias!)