It helps with this organization that it's national, it exists for many years. Technically it's a whole bunch of organizations united during big disasters. Organizations like the Dutch Red Cross, Oxfam Novib, Unicef etc. and they work together during disasters like the tsunamis in 2004, the 2010 earthquake in Haiti, the drought in South Africa in 2011.
Usually on one day they try to gather as much money as possible, with marathon tv or radio shows. All kinds of communities, churches/hospitals/schools/sport clubs etc., who collect money by having a fair, yard sales or selling cookies. Matching campaigns are popular among companies. My own company said: "E-mail how much you have donated to the organization to HR, the total amount will be matched (doubled) by the company."
It is a well known organization, but of course people are skeptical if the money ends up in the right place. And for that, usually the national press helps by explaining how the organization works and how they make sure the help / goods / money end up in the right hands.
Today, with all the different collections, over 40 million euro was raised by the Dutch public (population 17.44 million people)