So its important to note that yes, while HST was the emergent leader of this approach to truth-seeking in journalism, they weren't alone in their searching. Take for example "The revolt of the cockroach people", which was written at the same times as "Fear and Loathing in Las Vegas", but after "The Kentucky Derby Is Decadent and Depraved", which I would argue was Thompson's first "full" attempt at Gonzo. So with "The revolt of the cockroach people", which interestingly, was written by Oscar Zeta Acosta, who is also the HST's 'lawyer' in Fear and Loathing in Las Vegas. So Thompson did definitely invent gonzo, but even in its infancy, he wasn't alone in his practice of the art.
So there are a few things to disambiguate: Who were Thompson contemporaries? Journalists or other people doing Gonzo? Then, following that, what was the general impression of Gonzo, independent of Thompson? Then you have to layer in the time period, specifically, i think you would need to understand the importance of magazines and magazine culture at the time, and the fact that HST was writing for Rolling Stone. Then there is the "freak" movement, and how HST/ Gonzo fit within that broader movement.
I can't really answer these questions for you, but I have studied Thompson and others who use the Gonzo approach, and I have written some medium length Gonzo articles myself. I'm willing to share some of my writing on a case by case basis if you DM me.