I've already seen tons of fujo fanarts before the anime was even announced
i dont know if I would use fanarts as a base to predict success, using [pixiv] [illustrations only]
world trigger is at 20K
promised neverland is at 1K
BLackClover is at 1K
kimetsu is at 4K
hinomaru is at 0.9K
food wars is at 5.4K
haikyuu is at 189K
heroaca is at 46K
based on this world trigger should be a flagship seller in jump, while things like hinomaru and promised neverland should be barely selling anything, clearly you can see that TPN is exploding even with an inactive fandom, food wars had initial success but stagnated.
That said it perhaps it indicates that Kimetsu is actually well aligned for success though, since is clearly doing better than its senior Hinomaru, and should overtake Food Wars soon, but being so close to Food Wars,one would think that its sales would actually be more in line with Food Wars, which it is like 75% below food wars.
With 3 anime seasons, Haikyuu!! was more effective at mobilizing its fans than HeroAca was with the same media attention.
conclusion: A small series can have a very active fanbase