Most people are desperate for structure, for a culture to belong to, for a place among their society. Western governments have, on purpose, erased that structure which in the West was provided by the Christian church, patriotism, and nationalism. These people look around for something to replace the void and there’s Islam waiting to fill their aching need.
It’s liberalism that puts up with it. No cure.
“Western governments have, on purpose, erased that structure”
You are correct that this is by design, to make one big economic zone called the EU. No national identity, just loyalty to one large government.
The people in the former Soviet Union found how that worked out, but they weren’t stupid enough to flood themselves with non-Soviet peoples.