Irc touhou is just a series of japanese games where you avoid some things on screen shooting at you.
Then how come it has so many fanfics? Putting aside the ridiculous number of hentai dedicated to the characters, there are even legit manga about it.
I just came across one called "the magician who loved a fake" and apparantelly there was another one by the same author "genjo-something of humans".
Question is, does touhou actually have lore? And what is up with all the fanfics?
Tbh, it was probably mostly a coincidence that Touhou's fandom became s big as it is.
The games are shmps, which are a fairly niche genre of game.
The in-game dialogue is also really small, and there isn't much character development in any of the games. The manuals that come with the game give you some more background lore on things though.
That said, the character's have fun personalities and cute designs, so it's easy to grow fond of them.
Then there are also official mangas that further develop the lore and the characters, which adds a nice charm to the series.
And of course... The soundtrack. Touhou's soundtrack is nothing short of amazing, and basically everyone that listens to it tends to love it.
And well... The fans just liked it? For one reason or another, Touhou is an insanely popular fandom. Lots and lots of doujinshis for it exist, and then there are also fan-made animes, games, fanart, and... music remixes. Lots and lots of remixes. AFAIK, most people from the west that learned about Touhou, learned about it from hearing remixes without even knowing that Touhou was a thing.
Touhou's fandom is big. I really think it was probably more luck than anything else, but there are certainly plenty of factors that contributed to Touhou becoming popular.
Oh, and if you wanna try getting into the fandom, I recommend the doujinshis from Satou Kibi (and since someone will ask. No, they aren't lewd). They're my favorite doujinshi author~