There are lots of things going in the Netherlands that help cyclist safety.
So much of the country cycles, that motorist view cyclists as fellow humans instead of annoying hipster trash delayed their daily commute.
There are so many cyclists, motorists aren't surprised to see them.
There are so many cyclists, bike lane and dedicated bike paths get built.
The Dutch rarely live even 20 miles from where they work. Typically, they live in the same city. And they shop in their own neighborhood. That means predictable routes from residential to work/schools that leads to bike lanes, etc.
Public transportation within cities, between cities, and between countries is great. So very few young Dutch own a car. A lot of Dutch families have a car only for the trip to Grandmothers and the annual August trip to the south of France. That makes the French tollroads and German autobahns pretty scary in August, but means more people on bikes and public transit 48 weeks of the year.
There are no hills! For miles and miles, the tallest thing I saw was a freeway overpass. And there was a sailboat(!!!), sailing in it (i.e. the overpass was a sea-level canal and I'd been below sea level for days). With no hills, bicycling is a lot easier and you never get going faster than you can pedal.
A lot Dutch cycling is done upright and at low speed. Sure, some people have nice racing bikes and ride them on weekends in masse like American yuppies go out on their crotch-rocket motorcycles on weekend mornings. But your leave-it-at-the-curb, daily-rider bike is a beater, often with handlebars for upright cycling - tall, moving at a predictable speed, easy for a motorist to notice.