Well, the country is pretty flat of course. Densely populated, with lots of interesting spots not far apart. Thus within reasonable cycling range.
But it is also blessed with a rather capricious climate. Often windy as well.
Still, for good reasons : yes indeed, the bicycle is ideal to discover the Netherlands.
To explain that, two keywords : infrastructure and social acceptance.
In that, Holland is still different from the neighbouring countries. Caused by the meanders of history. If you want to know more about how this came to happen, read this cycling history page.
The result is a well organised system of bicycle paths and routes that makes a bike friendly environment. The more bicycle traffic is separated from where cars ride, the saver for bicycles, naturally.
A bicycle is also perfectly practical for visiting these small historic towns, with narrow streets. No parking problems either.
After all, these towns simply were not made for cars.
And especially on the countryside, and in the many natural parks (you'll be surprised how much of that there is around here), a bike brings you to places were no car can come.