From what I read there was a shift in the 1950s from an intellectual interest in pagan myths to a serious form of religion.
That's part of the story, I believe. Certainly, Kenneth Grahame, C. S. Lewis, J. R. R. Tolkien, Percy Shelley, etc., were not (neo)pagans, yet like many other authors their writings featured multiple motifs, characters, entities, and more borrowed from Greco-Roman authors. For those like Lewis and Tolkien, we find serious scholarship alongside fiction.
However, the 19th century was also marked by the production of grimoires, "secret" orders, and the development of magic frameworks (e.g., mappings from macroscale to microscale, incorporation of kabbalah, among other things) as well as a lengthy tradition (going back before the 19th century) of at least borderline religious druidic revivals.
I have no doubt that people before this time had interest and that some people seriously saw themselves as pagan but by the 1950 there was clearly an change in the number of people becoming pagan and a growing diversity of pagan faiths.
I wouldn't use that date, but rather the one you use below at the earliest, as by the 50s and early 60s the new religion(s) were pretty much all wiccan, and the druidic revival has a very long history (see e.g., Hutton's
Blood and Mistletoe: The History of the Druids in Britain) that the 1950s had no real effect on.
By the 1960s variations of wicca were developing as well as people practicing Celtic/Druidism, Germanic/Heathenry/Asatru, Greek, Roman, and Egyptian paganism.
Variations of Wicca, yes. Same with Druidism. However, I'm not so sure about Asatru and the others. (Neo)gnosticisms, Norse paganisms, even witches (i.e., the various groups of people who did not identify themselves as wiccans but did identify themselves as witches) were, I believe, not until the 60s at least. I could be wrong as I'm going off of memory here so I'll have to check up on this one.
What happened to cause this change?
That will require another post.