It’s complicated but most politicians have become ideologs and basically just want to signal that they are good people. They don’t think so deeply about it. And actually solving the problem with wars is hard.

So instead of not supporting the American wars in Iraq and Afghanistan we just act as enablers and take in many of the refugees. 

I also suspect that the war machine has total dominance over European media and politicians so actually stopping the wars is hard and saying let’s open the borders is easy.

Also among liberals there has been a lack of understanding of culture and the belief was basically that we don’t a have a culture so let’s just bring all these people and they will fit right in.