Going by the numbers presented in this article, it's actually Denmark. And our bike culture is mostly a feature of Copenhagen, so really Copenhagen is the global hub.
Cargo bikes were always quite popular in Copenhagen. The dominant brand for several decades was produced in Christiania (a hippie/anarchist commune), so just a few years ago they were all still known as "Christiania bikes" in Denmark. I think the more recent addition of electric assists made them explode in popularity and other brands became more popular.
The dutch don't seem to be very into cargo bikes. They certainly do exist (bakfiets are pretty famous, and the reference), but the vast, vast majority of the parc seems to be more of the granny bike variety, possibly with panniers and child seats, rather than dedicated cargo.
E.g. in BicycleDutch's station area video, while it was not 4 uninterrupted minutes of bike traffic around utrecht's station I only noticed 3 cargo bikes.
I don't understand this about the Dutch people. So many old, granny bikes, that are so heavy, with steel fenders, steel stands etc. So heavy, inefficient.
So many cyclists with their chains screeching loudly, as if they haven't seen oil in years. So many broken chains around the streets and bike paths. So many with terrible lighting, cheap flickering LEDs that are barely visible. Or many young people with no lighting at all.
In comparison, the Germans seem to invest a lot more in their bikes. A lot more expensive bikes, and generally a lot better maintained.
The bike theft arms race is a race to the bottom: if you want your bike to loyally wait for you where you left it you need to make sure that it looks worse than its peers. A nearly broken bike that is there when you need it has far more utility than a neatly maintained one that isn't.
> I don't understand this about the Dutch people. So many old, granny bikes, that are so heavy, with steel fenders, steel stands etc. So heavy, inefficient.
Cheap, reliable, low-maintenance, unattractive to thiefs. When you drop your bike at the train station you don't want it to stand out in a sea of other cheap bikes.
And with bikes generally getting priority, the weight is likely less of a concern.
I (also German) didn't do the math and gave it the benefit of the doubt: "well, maybe in Copenhagen and Amsterdam the market is already so saturated that a momentary fashion wave of Germans catching up might nib sales slightly ahead for a short while". Apparently not!