To be honest immigration happened forever because people look for a better place to live. The able, hard working and entrepreneurial ones bring a lot to the countries they immigrate to. So, I do not see immigration as "a problem".

Additionally Europe's natality is not great, it needs people working. So many enterprises in Europe are happy with that.

Why is immigration presented as a problem? Because it is easy, does not affect directly any potential voter (I mean, if you say "rich are to blame", around half of the voters will not vote you, if you say "the poor are to blame" the other half will not vote you, but immigrants? No problem they generally don't vote) and because Europe has a tradition to seeing itself "above others". So if there are problems and you see dark people around, must be there fault, no? I really think they are (many) people that think like that (and I also met a couple)...