BR et al,
You can ask as much as you like, but the answer is always the same: they believe in "God" because a book they choose to believe is correct tells them to. That's it: there's no argument, no evidence, no anything beyond that circular reasoning. The closest they will ever get to breaking the circle is to look for imaginary holes in the science so as to jemmy their god into them, but that's it.
Really, that's it.