Fanfic culture as we know it today owes so much to older fans, especially older women, who were obsessed with The Premise.
This was a world before widespread internet, before sites like fanfiction dot net let alone anything like AO3, and long before queer media became more widely acceptable. The Hays Code, which forbade Hollywood from depicting “sexual perversion” which gay representation was considered, was only repealed in 1968, and many still unofficially stuck to it and that part especially for longer. Original Star Trek was canceled in 1969, the same year as Stonewall. But in the early 70s, fans were collaborating and making fan zines containing writings about The Premise, distributing physical copies at conventions and creating mailing lists. Later came private email chains.
In a world with so many factors working against it, large groups of fans decided they were so invested in the idea of these two men together that they would MAKE ways to share their work and acquire new content from others.
Transformative fiction existed in ways before. Adaptations of other stories have existed about as long as stories have, and I’m sure people had written their own little reimaginings and “headcanon” side stories for themselves and friends before. But the culture of spreading it far and wide, of collaborating to do so… If it hadn’t been Spirk, maybe it still would have developed similarly later/slower, but we can’t be sure. In the world we have, though, we owe old ladies who loved The Premise everything. 🙏