Exhibit 9726489 for "Your favorite authors did Touhou doujinshi before they drew their own series."
I swear that its some sort of requirement at this point. Not that I mind but it still blew my mind when I learned the authors of Bloom Into You also drew Touhou manga at some point.
Touhou was huge back in the 2000s and early 10s, and fan conventions were a great place to exhibit your art, meet fellow authors, and get some vital experience before branching into original work. I'm not much of an expert with regards to art, but I'd argue that ZUN's brilliant character designs would probably be really fun to replicate and take inspiration from, and the same goes for the immensely entertaining cast and unique setting. Touhou just lends itself to speculation, fan creations and headcanons better than any other series I've encountered, while still maintaining an incredibly unique and distinctive identity, which is why you'll find nothing quite like it anywhere else in the world. Even now, when other, more accessible franchises like KanColle, Azur Lane, FGO as well as Love Live and BanDori have soared to incredible popularity, drawing Touhou art is still guaranteed to grab eyeballs and help you make a name for yourself on online platforms. The fact that the series manages to command such a loyal and dedicated fandom despite not having any official anime adaptations, major corporate sponsorship, or gacha games filled with drip-feeds of content and pandering is a testament to it's quality. In Touhou, the fans aren't just consumers, but active participants to an incredible degree, and the body of work they've produced over the years is, in my opinion, far more engaging and diverse than anything a single team of hired writers could ever achieve. In an age where the market is dominated by media specifically designed by suits and algorithms to pander to the fantasies of various otaku demographics, Touhou still retains that fiery, 90s-era indie-game spirit, and I think that's an actual goddamn miracle in today's world.