There are at least a BAZILLION different Christian denominations each of which believes it is superior to all the others. WHY NOT JUST ONE?

Are there different denominations of Buddhism? I think there are several Jewish sects one of which is Reform? How about Islam? Are there a bazillion denominations there too or just a couple? Why the need for so many VARIATIONS ON A THEME OF JESUS? Why the offshoots and upstarts and manipulations?