They need migrants so that they can continue to have a platform on xenophobia. Their voters can’t connect the dots, they will just vote for whoever signals a “hard course against migrants”, regardless if their actual policies will result in more immigration.
I really don't like how the article (like so many others) uses the term "illegal migrants" for "asylum seekers". Entering an EU country seeking asylum is a priori legal. That's the entire point of asylum law.
This is particularly bad when the descriptor "illegal" is applied to the person ("migrant") rather than the act of entering a country ("migration"). Humans can not be illegal.
"Undocumented" or "irregular" are the words to use in this case.