I would disagree that Gerald Gardner did not create Wicca.
Certainly there is concrete evidence that Gardner was initiated into a group referring to themselves as Witches or "of the Wica" in December 1939. However, Gardner points out from the beginning that this group failed to meet his expectations of what witchcraft should be about. He was basing his expectations on the writings of Margaret Murray. And when he wanted to go public to draw in more members he was told that he could not. At that point Gardner separated himself from his initial coven and began to develop a more cohesive Tradition using input from Masonic rituals, ceremonial magick, folk magick, etc. In addition, much of the liturgy was created by his first HPS, Doreen Valiente and added to by subsequent High Prietesses and Gardner himself. Thus what Gardner created and what we today refer to as Wicca was a far cry from the original group into which he was initiated. And so it appears only fair to state that Gardner did "create" that which is today called Wicca.
In the beginning Gardner referred to his practices as the "Cult of Witchcraft" and to its practitioners as being "of the Wica". However, Gardner was familiar with the Anglo-Saxon terms for Witch, being "wicce" (female witch) and "wicca" (male witch). And by 1961 Gardner himself was referring to his practices as Wicca. You can see him use the term in an interview in 1961. http://www.thewica.co.uk/daymet.htm
I would recommend the following books on the history of Gerald Gardner and Wicca:
"Triumph of the Moon" by Ronald Hutton
"Gerald Gardner and the Cauldron of Inspiration" by Philip Heselton
"Wiccan Roots" by Philip Heselton
"Witch Father, A Life of Gerald Gardner" Vol 1 & 2
"50 Years of Wicca" by Fred Lamond
"Lid off the Cauldron" by Patricia Crowther