[...] but the act of picking a partner immediately makes them more special than any of the thousands who may be just as pretty/intelligent/smart.

That is because the act of picking is what makes them special. If there were two exact clones of a person and I chose to marry one and not the other, my new spouse is more special than the extra clone.

To carry this back to the original comparison between the Bible and LotR, the Bible is sacred because people believe it is the One Way. The act of believing is what makes it sacred. This carries into the celebrity example as well.

The irrationality comes when someone thinks the causality is running the other way. Someone who believes in the Bible because it is sacred has the cause and effect backwards. Likewise, if I married my spouse because she was the most special I am being naive.