As for the sculpture of Moses on the east side of the building, my_kids, when you were rejecting the most popular answer and checking it out for yourself, did you bother to find out what
the sculptor himself says he meant by it?
“Law as an element of civilization was normally and naturally derived or inherited in this country from former civilizations. The “Eastern Pediment” of the Supreme Court Building suggests therefore the treatment of such fundamental laws and precepts as are derived from the East.
Moses, Confucius and Solon are chosen as representing three great civilizations and form the central group of this Pediment.
Religion had nothing to do with his choice of Moses at all.