good post. Ive been thinking about this also.
I laughed at some of the comments.Like that guy with his evolution theory..and couple of americans switching to defense mode because of the "americans dont like to kick"comment)) and not to forget the ganja post! ganjabas)) they even found it in Shakepears basement..think there could be a corelation between ganja and talent? lol, everything is possible))
Seriously, there isnt just one reason. It must be a combination of couple of them.
Im not ethnically dutch but ive been living here for 9 years. Iow, i had the opportunity to observate how things work here.
the combnation of reasons i talked before in a row:
A) Dutch are sportive. This is a fact. In this land people start sporting at a very young age(5-6 y old). They start young with sports like football, swimming and judo. The dutch like cycling very much

theyre so passionate in it, that the infrastructure is adjusted to cyclers.( you can see "garages" for cycles everywhere, for example)It is also considered normal to cycle near automobile roads(roads for cyclers are colored beige). You really cant find a place in Holland where people dont cycle on roads. And you dont only see young and middle-aged people on cycles but also a lot of seniors.
B) IMHO, the fact that dutch eat a lot of cheese and like to drink a lot of milk(more at young age, when the physical fundament and structure is being set) has to do with the "hard legs" moment. Milk and yellow cheese deliver a lot of important minerals(like calcium) to the young body. It hardens the bone structure. One could argue this one, of course
C) Dutch mentality. If i said that ive never seen such a disciplined nation as the dutch, i wouldnt be exagereting. Theyre very hard working. Hard working and disciplined.
D) I think A,B, and C combined with the reasons stated before me, are enough for now..
Excuse me for my bad english..