Yes, ‘they’ know mass migration destroys civilizations. First the chaos and then the order (Genesis 1:1-4 in Hebrew illustrates this better than in the English transliteration).
Ecclesiastes 1:9-11 (NKJV)
That which has been is what will be, That which is done is what will be done, And there is nothing new under the sun.
10 Is there anything of which it may be said, “See, this is new”? It has already been in ancient times before us.
11 There is no remembrance of former things, Nor will there be any remembrance of things that are to come By those who will come after.
Quoted because it is worth repeating.