A lot of Muslims leave their faith because of dreams of Jesus. God likely does that to them with that method because they believe the creator uses dreams to talk to us. I know one and she surely believes. She simply had to find a bible at the store and she was set. Her family hates her, but that’s not important. Edit: of course you are correct we don’t know who will stay in the faith—we often don’t know who is also just pretending. Thats to be sorted out by God at the end as you know.