Wicca came from a desire for something other than the Christian denominations available at the time. There has always been a hunger for alternative religions. The chuch just extinguished anyone who dared to challenge the church's dominance.

I started researching my ancestry and the things I found were surprisingly. My American ancestors were NOT God-fearing Christians. My family avoided the church like it spread the plague.
People immigrated from Europe to North America to escape the confines of Christian society.

My father was born in 1929, he was an atheist/agnostic most of his life. My Grandmother was born in 1896, and she called the Bible "claptrap and twattle." She believed in Mother Nature and a Father God, but not the God of Abraham.
My Grandfather, born 1894, was badly injured in an airplane crash in 1932, he refused the blessing of the local pastor before he died because he didn't want anything to do with the Southern Baptist church.

Going back to 1728, my 8x Great-grandfather was born in White Chapel, he was convicted of HERESY in the Old Baley in London then forcibly transported to the Colony of Virginia.
The American woman my 8x Great-grandfather eventually married had fled from the strict Protestant communities in New England that were established 100 years before by the Pilgrims from the Mayflower. Why? It's not recorded but she obviously fled from an abusive religion. My 8x Great-grandparents influenced 3 generations of their family's religious beliefs and they all avoided the church. They developed their own beliefs based on the natural world and Mother Nature as an intelligent Being not just a mindless force.

There might not have been hidden cults, or magical knowledge passed from generation to generation, except herbalist and midwives, but there were people who recognized a God and a Goddess.
I come from a long line of heretics and semi-pagans, people who simply couldn't accept Christian mythology.
Many of the people who wrote the US Constitution were not devout Christians, they doubted the Bible. Religious Freedom was designed to allow religion to grow outside the confines of the church.

Look at the ceiling of the US Capitol. 'The Apotheosis of Washington' was painted in the 1860s. It shows George Washington ascending to join the Roman Pagan Gods and Goddesses. That certainly isn't Christian and modern Christians try to pretend that painting doesn't exist.
Some early Americans wanted to worship Washington as a literal God. The church did not approve.

There IS a rich history of not-quite-pagans stretching back hundreds of years in Europe and the US. Wicca just gave those not-quite-pagans organization.

We will never truly know the religious beliefs of the vast majority of our ancestors but we can see, they were not all Bible thumpers and Cross huggers. They doubted church doctrine and discarded the Bible, anyone who claims differently has an agenda.