Follow the money indeed. The first waves of massive immigration were required to conquer, settle, and hold the entirety of what is now the US. It was a great replacement of the native population. This was profitable for many, more for some than others.
Then immigration was required for cheap labor. This was profitable for many, more for some than others.
Then immigration was required for cheap labor, ignorant votes, and and to divide the US. This was profitable for many, more for some than others.
Then the US was no more, and the glorious one world government took full control. Migration and movement became very tightly controlled. Only those with a high enough social credit score were allowed to move or travel. This was profitable for many, more for some than others.
History doesn't repeat itself, but it often rhymes.