I'd say the majority of monotheistic religions are pretty samey too. As mooney suggests they are 'apparently' different, but usually, often, not. Even if those in positions of power and influence in the various 'official' brands don't want it to be so and create violent conflict with others.
Potentially it (religion) comes from the same place, deep at the back, where the sense of self and other and empathy all come from. Perhaps it's part plagiarism, part a glimpse of some deep singular truth. Science not being able to trace something doesn't mean it's not true, to state the patently obvs.
Reading up on a bit of the old Zoroastrianism at the moment, fascinating, and all very familiar.