Once the region gained political organization, primarily from outside countries, the people used their open mindedness to advance their knowledge and expand themselves. It didn't take long for the Dutch to shift from a lifestyle based on the lands to one based on the seas as they became a world power as they established colonies in Asia, the Americas, and elsewhere.
The opening of the Dutch people to the world also introduced new ideas and cultural aspects to the Dutch. Many people willingly learned more and adopted many of these foreign introductions. This time also later encouraged the immigration of people to the Netherlands, particularly people from their former colonies. This made the country more diverse, but again the people readily accepted these differences and often encouraged new foods and ideas.
Today the Dutch remain a very welcoming society, but it's an openness that doesn't come with open arms; it's a welcoming attitude that accepts differences in beliefs, dress, languages, foods, and more. While the Dutch are very welcoming and accepting, they still strongly value their individual privacies and freedoms. It's rare to see the Dutch gather in large social outings or to unite in huge numbers (other than at speed skating events in the Winter Olympics), but they respect each other and each individual's personal lifestyle and beliefs. The Dutch rarely judge others and almost never brag about their own accomplishments or characteristics. They accept differences and expect you to do the same without judgment.