Most populations shifts, for instance Europeans coming to America, are caused by immigration. Governments sometimes encourage immigration because they need more people, mostly to replace native populations.
Today, most immigration comes from Moslem countries to the once Christian countries that have developed large-scale, and now, suicidal, welfare programs. Arab countries encourage and subsidize this because it gets rid of people who might otherwise take to their streets, demanding more distribution of wealth.
The easiest way for wealthy Arabs to get rid of those troublemakers is to export them to the West. That solves the immediate problem of getting them off their streets while destabilizing and impoverishing the countries in which they settle. Lots of bribes are necessary to get elected officials in the West to destroy their own nations, but they work.
Spending time in any international airport shows how effective those bribes have been. Incoming planes disgorge endless numbers of foreign peoples, all of whom have places arranged for them to go. National borders in the West are now a joke, an open door to all those taking advantage of the bribed officials whose actions encourage the destruction of their own nations and neighbors, in the name of “fairness” and “diversity”.
We may look at them as potential converts to Christianity, but that’s made difficult because they move into neighborhoods that are organized to keep them from seeing those in their new countries as anything but enemies, to be destroyed. Ever more quickly, they turn into saboteurs. But, what else can we do?