You can see the realization dawn on them.
Just so you guys don't throw shade at me for xEnoPhoBia or what else, I'm gonna throw a quick masterclass in Islamic eschatology (end times theology) at ya. Muslims believe that the entire world must submit (what "Islam" and "Muslim" mean) to their religion in order for the end of days and the final judgement of God to come.
They believe it is their duty to struggle ("jihad") for this cause, because they believe that heaven-on-earth will not come until the whole world has been subjugated to Islam. At that time, Jesus Christ and a figure named the "Mahdi" will return to usher in order and peace for all people.
This borrows from Jesus, who commanded his followers to make disciples of all nations, but the Christian hope of forgiveness and adoption as the sons of God is much different than the Islamic notion of subservience and servitude. The Muslim god is vastly different from the God of Jesus, Abraham, and Moses.
If you don't believe me, go spend some time living in the Middle East as I have. Learn Arabic as I have. Live with a Saudi roommate as I have. Teach hundreds of Muslim foreign exchange students as I have.
I've had many Muslim friends, but they do not hide this fact: That their mandate is to conquer, and outside open war, immigration is an effective way to win a nation. One primary "weapon" is having lots of babies to outcompete the infidels.
Europeans are realizing this fact about 30 years too late, thinking this was about skin color when it was always about theology.
(And Europeans threw in the towel on theology a long time ago.)
But no matter. The Gospel always wins.