My mother was an accountant who started school taking pharmacy, and represented herself in court numerous times even winning against the oil companies. Her favorite hobbies were mind puzzles, crosswords, sudoku, etc. Yet she was christian, and believed in reincarnation, practiced palmistry, and handwriting analysis, as well as she had a quija board...

Inversely I have met some outright dimwits who happen to be atheists or agnostics. So it's not as simple as smart people reject supernaturalism and only lower intelligent people believe or have faith

Even if they are smart doesn't mean that they are confident. There are people in this world who cannot fathom that we are not so special and that when we die that is it.