The functionalist theory of religion elucidated by rrteacher is a compelling response to this question, in my view, especially considering the considerable variety of world religions, past and present.
Believers of one religion, along with non-believers, often have a hard time relating to the actual views and matters of faith expressed in other religions. The beliefs of one faith can seem quite odd to people of another faith.
However, the will to believe is relatable across religions, despite the truly amazing things that many religions hold as central tenets of the faith when viewed from outside of the religion, so to speak.
What can explain to the outsider or non-believer the mental mechanisms that underpin a "foreign" faith? I think the functionalist theory provides a rather compelling explanation.