Even intelligent people can have their limits. Einstein was pounded by zealots on both side and chose to take the middle ground. He was a Jew, influenced by Catholicism as a child. A reader of Immanuel Kant and Spinoza. Spinoza's work was classic but it took a century before it was recognized, because of his religious position he was dashed by the Jews and Christians.
One cannot possibly be brought up in a environment of religion and not be influenced by it. So Einstein was open to the idea, rejected by both sides which was a good place to be in his time. It was unreasonable to defend a religion while you were dissecting theories held by believers and to discount believers while trying to convince them that his ideas should be considered.
