The "true" religion is whatever gives you peace in times of pain, helps guide your actions so you live a life that limits the suffering of yourself and others, and gives you the motivation to wake up every day and contribute to the world in a meaningful way.
The native Americans, central and southern africans, australians, and pacific islanders lived for thousands of years never knowing anything about Jesus, Mohammed, Buddah, Zeus, Rah, Moses, etc. They lived and died with their own understanding of their existence, their own interpretations of good and evil, and their own cosmology. Humans are wired to want meaning. It is the reason almost every child at one point in his or her life will start asking "why?" constantly when they learn what that word means. Language itself is something that evolved from the human need to assign meaning to things so we can communicate and understand.
People come up with explanations that make sense to them or they get vivid dreams or visions that fill in the blanks. They then go from there and hold on to those beliefs because it works for them. The idea of believing in a "true" religion while others which are just as old if not older are "fake" is a sign of childish narcissm and the desire to find value only in defining what you arent, rather than embracing what you are and what works for you. People who obsess over trying to invalidate other's belief systems betray a deep insecurity and fear they feel around having made the "wrong" choice. There is no wrong choice. Whatever you believe in strongly with everything you have, someone else believes something completely different with that same level of devotion. Understanding that and accepting that is a key part of growing up and being a mature adult.