They saw what happened in other EU countries where guilt-ridden citizens don't have any respect for their own county anymore, and were not looking to repeat their mistakes.
The vast majority of immigrants are economic migrants that have no right to ask for political asylum, and were let in by left-wing government who—contrary to popular belief—are now hand-in-hand with big companies rather than looking out for workers, and kept letting them in just to keep salaries low and make their masters happy.
Back when I was a kid in Italy I used to pick grapes for something like 15/h, now there are Africans that do it for 4/h and are literally treated like slaves. Very sad.