Statistically there will be weird coincidences completely naturally. It's also quite arbitrary which we see as meaningful. If say, Linux networking has unusually many people called "John" that probably will be unnoticed because nobody pays that much attention to common, unremarkable names. If they all randomly turn out to have green eyes, then that's more visible. It's completely subjective which of those is more remarkable.

There are also likely social effects -- people stick together, and some side interests align with some fields. Eg, I think it's reasonable to guess there's going to be more furries than average in VR development. Part because VR allow you to look like whatever you want a lot of the time, part because people will invite their friends in.