They were always just biding their time until there were enough of them that they could organize themselves. Putting on a mask and pretending to be something they aren't, weren't and can never be.
It doesn't take much to fool the children of the Western world. Just like Adam and Eve with the serpent in the garden, they are naive and gullible.
They are only coming here for a better life, you see. It's so violent and insane and depraved and horrible back where they came from. Nobody seems to know why. They are just trying to get away from that back in their home and besides, most of them have no luggage. They are only carrying themselves. What's the worst that could happen?
We'll live by your law today, pinky. Tomorrow will be another story, on that day we'll live by our law ... which incidentally, is much simpler than your law. He who has the biggest machete makes the laws where we come from.
Vault-Co predicts you will see many, many similar movies with the same villains and themes coming out in the new Amerikwa. After all, there is now a large enough audience to support them.