Germany has a large Turkish demographic that the governing class is intent on expanding on that does not mix nor integrate, even after 2 or 3 generations. This culture encourages their women to procreate at a young age, denies them their own agency and forces them to subside on benefits.
The same is true in the UK with Pakistanis / Bangladeshis, with more than half receiving state support [1]. I'm not sure if Germany has towns like Bradford [2] or Luton but I'd wager this was the deciding factor why the Brits voted out, given that the majority of refugees during the crisis were from Islamic countries. Current trends will see Britons in the minority by 2066 [3].
I was in Berlin not too long ago, and as myself and a few coworkers returned from lunch near Spandau, a middle aged woman in full dress stopped in the middle of the road and dramatically traced a line along her neck whilst staring directly at the four of us. Not the behavior I would expect from someone grateful to find themselves in the country of another.
I have no idea why Western countries have persued this policy, or allowed the funding of mosques by foreign actors. I know in the UK there was a scandal that suggested that the Labour party might have done so to increase their voting base [4], but with the spousal rights that immigration brings it's been extremely difficult to get a handle on ever since. In the case of Germany, since infinite growth is impossible, will the loss of societal cohesion in persuit of GDP alone prove worth it?
Peter Thiel predicts the future of Europe is to either islamicize or become surveillance states [5]. For an example of how this might play out over the long term, Lebanon used to be a Christian majority country until it accepted a large influx of muslim refugees. The place has been a smoking ruin ever since, with Islamic culture imposed and Christians fleeing a nation created specifically for them by the French. Sadly the west in it's infinite wisdom decided to subsequently destroy the one country that might have provided a natural refuge for these people [6].
[1] https://www.ethnicity-facts-figures.service.gov.uk/work-pay-... [2] https://datashine.org.uk/#table=QS201EW&col=QS201EW0011&ramp... [3] https://www.telegraph.co.uk/news/uknews/immigration/8142176/... [4] https://www.telegraph.co.uk/news/uknews/law-and-order/641845... [5] https://www.youtube.com/watch?v=iRleB034EC8&t=38m51s [6] https://www.wikileaks.org/plusd/cables/1976BEIRUT02937_b.htm...