I'd venture a different theory: Germany and Italy were not unified and pacified states at the time (and Switzerland is tiny and doesn't have a coast). In contrast, the European empire builders, Portugal, Spain, Netherlands, and the UK were unified, pacified, reasonably large/wealthy and sea-faring.
The Netherlands are tiny and a very young country at that time surrounded by much stronger neighbors. With a good fleet defensible though since a lot of parts can be flooded to prevent invasion.
