The Dutch were confined to living there, it wasn't really a funny choice or coincidence.
The various Shogunates of the Edo period were extremely isolationist and generally completely prevented any foreigner from setting foot on Japanese land.
After an attempted rebellion of Catholics, the Portuguese (who had been doing a lot of missionary work) were entirely expelled in 1639, and in 1641, the Dutch were forcibly relocated from the port city they had been mostly established in since 1609, Hirado, to Dejima, the pictured artificial island.
From 1641 to 1854, Nagasaki, which Dejima is a part of, served as the only legal port for Dutch and Chinese vessels to dock.
Dejima itself was the only legal place for the Dutch to actually live in Japan.
The Dutch were not allowed to enter greater Nagasaki, they were treated as second class citizens, under tight supervision, forbidden from discussing Christianity.
tl;dr The Dutch didn't just all decide to settle on Dejima, they were forcibly relocated there, living under armed guard, not allowed to possess Bibles nor hold religious services.