While a homogenous hard-working population helps, it just delays the inevitable; the savages were imported into Sweden for the same reason the US imports them: a negative birthrate among the native population. Now when they trumpet a higher US birthrate, you have to note WHO is giving birth - they are now considered “Americans”.
Few people have a work ethic like Germans, yet even they were importing people decades ago (Turks in West Germany, Vietnamese in the communist East); for many years Ireland was the last Western European country with a birthrate that would replace its population, and they may not even have that anymore.
Your point is a good one. Some of this is the result of unintended consequences. The ripple of effect of birth control and worse, abortion, comes to mind.
Why is abortion being so heavily sold in Ireland?