Could be many reason I guess (after all, there's only 5.5 million Finns around), but the map is a bit pointless IMHO because it only counts university and research lab projects. Most recent languages I'm aware of (and which are actually useful in the real world) had been started by individuals in their spare time.
Rust, Zig, Odin, Nim are probably the most popular. It's also not surprising IMHO, most software is created to scratch a particular itch of an individual. Also specifically for programming languages, LLVM made it possible for individuals to build their own pet language with relatively little effort
but still get competitive performance and target platform coverage.
Rust though didn’t gain traction until Mozilla adopted it. I guess we could say individuals always created programming languages but majority are sponsored and paid by orgs/companies.
Before LLVM it was much harder for individuals to build competitive programming languages though (edited my original post with that afterthought, apologies)
It lists languages designed by commercial companies too.
The main reason it avoids showing languages created by individuals is that it can be hard to narrow down their location. Also, it would count as doxing.