The psychological halo effect is a cognitive bias where our overall
impression of a person influences how we feel and think about their specific
traits. The halo effect can strongly contribute to religious figures or
celebrities being perceived as having special authority or knowledge, even
outside their actual expertise.
Our brain may unconsciously generalize that if they’re admirable in this way,
they must also be wise, insightful, or correct about other things.
One reason for that is our own pride - we make them a celebrity in our own eyes and don't want to be wrong. And we feel less responsible for supporting or enabling stupid, false, evil or harmful views if those views have been expressed by somebody we make important. Implicitly, we are ready to blame them not ourselves.
Human kind has always had idols - a religious idol may not look like one.
But to treat a person as someone with special importance or knowledge is tacitly
religious. Most pagans remember had gods and goddesses they did not pray
to or sacrifice to but who were still deified by them. We all wish magic were
true and that leads us to invest some people with some magical authority or
knowledge.
The brain prefers coherence and it often feels uncomfortable to think - so you
outsource the thinking to somebody else. For that reason, you may distort
evidence or ignore evidence. You dodge the truth that the person is
brilliant in one area but uninformed in another. So we smooth it out into
a consistent positive image. This is closely related to authority bias,
charisma bias and the guru effect.
God belief implies it is possible that some people really do have spiritual gifts and know what normally cannot be known. It does not help.