Looking at their "About us" page two of the cofounders have extremely Dutch names so it's probably just where they started out.
Two of our founders, (we were seven, 2xSE, 1xUK, 2xUS, 2xNL) where based in NL. They also had great connections to the government in NL that supported us to get started. And we were initially part of a project which was based in the NL.