If a religion is born, and did not exist before, it only makes sense that someday it will die. Why are there are more stories about births of religions than deaths?
One related question revolves around how a god is kept alive. It is hard to have a religion if its god has died. So, is a god kept alive because a significant number of people believe the god exists, or, is it kept alive by ritual, a significant number of people praying to it?
An interesting metaphor of the god business is provided in the link. It is that there is a desert covered with gods all crying for attention. Those that get prayed to grow, the others die away. Do gods need to be prayed to to exist?
On the North and South American continents, gods have disappeared or died in recent centuries. These are gods of the people Christians conquered. There seems little if any remnants of the various Aztec gods following the Spanish conquests. Could we say the gods never existed, did exist but died or still exist but are not prayed to?
I would agree with the link that the biggest competitor of any religion probably is another god, not rationality. Gods seem to push aside rationality in most minds.
History tells us Christianity, like all other religions over time, has a shelf life and will be gone someday. Just what will happen to its god and why we don’t yet know.