This isn't exactly very big. Like think of a sub group of nerd culture.
If you want to know what is actually mainstream popular, look at commercials. It sounds odd but in Japan being in an ad is a sign of popularity and distinguished fame, versus the west idea of selling out. Basically the idea is, wow X must be real big for Y company to pay them to sell their product.
It's a long running thing to look at American actors doing Japanese commercials. My favorite is Tommy Lee Jones doing Boss coffee.
Some other examples are Pop Team Epic did ads for companies like Docomo cell phones. Undertale was used in a Japanese wrestling promotion by Kenny Omega. Gucci I think got Square Enix to let them use Lighting in ads. Tom and Jerry have also appeared selling toilet paper, I recall seeing once.
Fanart is nice to see niche sub group fandoms, but if you are curious about the regular Japanese person opinions look at commercials or of course sales figures.