I wonder why. When I think "PVV voter" I, maybe ignorantly, think of older people living in places that don't even have a lot of these immigrants/Muslims/etc. people to begin with, and that all they hear about these subgroups is on the news/media, which they disapprove or even irrationally fear.
But young people...
It is easy to dismiss him, but he addresses legitimate concerns that many people agree with. Many more than actually vote for him, because he is lacking solutions. This is not the US, where issues with migrants are mostly made up.
Large quantities of Muslims have entered the country, and there have been no successful attempts to integrate them. Many have kept horrible attitudes against women, gay people, jews and mostly non-muslims in general, have poor chances in the job market so they stay poor, flock to the same areas and are very heavily over represented in all the violent-crime statistics. They are on average also a lot younger than native Dutch people, so young people run into them much more often to experience this clash of cultures. The immigrant population is large enough, and the problems serious enough that there are probably hardly any dutch people who don't know anybody who's had some negative personal experiences.
Unfortunately a long time to not 'feed into racism' the traditional parties decided to simply ignore any issues and do nothing to try to integrate newcomers into society, prepare them for regular employment and stop ghetto-forming. Even during this election cycle on of the party leaders expressed that people are just convincing each other of problems where there are none.
This is not the way to go forward, ignoring problems does not make them go away. People should be offered a choice of either 'integrating the immigrants into society' or 'forcing the immigrants to comply'. Right now they have the choice between 'pretending nothing is wrong' or 'forcing the immigrants to comply', which to many people simply isn't a choice.
Old people are generally more pragmatic, will see that Wilders' option doesn't really help and decide to stick to their old parties. Young people are more idealistic and willing to give something a go.