bring millions of people you cannot integrate -> let them run amok -> gain convenient excuse to clamp down on privacy and add more surveillance -> slowly become a dictatorship due to people giving up their freedom for security (from the consequences you willingly created)
It's the UK formula again.
Bonus points: you also decrease wages and increase rent and house prices doing this, so you basically keep winning in your gated communities
What exactly would the end game be? resetting the clock to the middle ages? I don't think this is all planned, I think people underestimate the shortsightedness of governments.