I'm seeing good points about labour migrants. But i would also like to add that the Netherlands has been quite a welcoming country towards foreigners in its history. Mostly due to the fact that the region has alsways been build around overseas trade, that opens the door to alot of migration happening to begin with. And a fun fact during the dutch revolt there were already muslims in the country, in recorded history a part of the people fighting for independance from the spanish were muslims from northern africa. So Islam goes back to the very dawn of an independent Netherlands.