This is as pointless as it is dull.
I'm doing what we sometimes call, "guessing," because I am not an immigrant.
You could have tried your hand at "guessing" too. All you need to do is think, "if it was me, why might I consider doing what these people are doing?"
But the sad thing about this "guessing" lark is that you can never be sure you're right until you check with someone who actually knows - in this case, the immigrants concerned.
Now, the internet is a big place and I am sure that, in the time it took you to type your initial query, you could have googled immigrants' reasons for coming here.
I mean, you did actually want an answer, yeah? You weren't just trying to provoke a row or anything?