this aspect of modern history seems to have been deliberately pushed under the carpet, if we want to connect the dots as to how this infiltration into western societies happened, most of the literature will be about "how" it happened but not "why" it happened. the "how" is visible, which is basically ruling elites of western capitals accepted liberal demands of refugees from west asia.
what we won't find is any evidence on is "why" this happened, there will be theories but not evidence. usually historical events have a flow and connecting dots in public domain, but not on this issue.
The "why" is the end of WW2, where many plebean men died in that war, who would otherwise be used for factory and manual labour jobs aside from the soldiery.
And this is besides the Soviets eating up eastern europe, so no white men from Poland to work in your factories.
Whoever remained, didn't help since wages ofc shot up since there are less dudes to go around right?.
And so the gora suit-boot class came up with the wonderful idea of immigration.
For prolific colonizers these migrants came from their now ex-colonies
Pakjabi and Kanglus and Caribbean n!ggers for the Bri'ish,
Algerians, Moroccans, Tunisians and assorted n!ggers for the French,
The Germans were not so prolific, so their imported "guest workers"( unironically called this as a part of a German govt scheme to import them ) came from their WW1 bum-buddy Turkey, and not the posh, coastal Mediterranean parts mind you, but from the 5 times a day namaz, goat-fondling central and eastern portions of that country.
And these guests never left, and so you have 3rd gen immigrants who don't speak Turkish but are PrOd TuRkS and Love Erdogan
This importation was like aids, and random countries like Holland and Belgium also got some of these green stocks.
So this is the biggest why, every >love for migrants bullshit ideology you see peddled today has it's roots in greedy suit-boot gandus funding Marxist social engineers in academia, media and politics just so they can have some cheeep labor back in the 60s and 70s.
Capitalist greed is the most fertile, nitrate enriched soil for the vilest weeds of Marxism to grow, rather than the dry, gravely dirt of Communist dictatorships