How is Paganism an offshoot of Christianity? You might be able to make a claim of Christian influence for more New Age syncretic types, but not so much for Reconstructionists and others.
Same for Scientology. What's that have to do with Christianity?
Every religion has multiple origins. Islam, for instance, arose out of a Pagan Arab clan; but it was strongly influenced by Judaism and Christianity. The vast majority of Pagans, or, more properly, "Neopagans", are of Christian background. The most influenctial of this diverse group are the Wiccans, who can trace their origins as a cult to
Gerald Gardner (below):
Gardner was influenced by the Rosicrucians and other groups; but his family background was Christian.
Gardnerian Wicca, or Gardnerian Witchcraft, is a tradition in the neopagan religion of Wicca, whose members can trace initiatory descent from Gerald Gardner. The tradition is itself named after Gardner (18841964), a British civil servant and scholar of magic. The term "Gardnerian" was probably coined by the founder of Cochranian Witchcraft, Robert Cochrane in the 1950s or 60s, who himself left that tradition to found his own...
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https://www.google.com/search?q=Gar...s=org.mozilla:en-US:official&client=firefox-a
Other Wiccan leaders, such as Cochrane, were also mostly of Christian backgrounds. Most Wiccans claim a thread of tradition to ancient Pagan religions, but there is little connection between the two. Baptists also claim a tradition back to John the Baptist, as a comparison; but that doesn't make them Jewish.
Concerning Scientology, this was founded by
Lafayette Ronald Hubbard, a distant relative of mine. His background was thoroughly Christian, and he attended Christian churches throughout his youth. He was a great storyteller, like his grandfather; and many to this day take his stories to be true.
Lafayette Waterbury, L. Ron Hubbard's grandfather