I suppose it was because of D factor, C factor, and C factor.
As for story-wise... Korean's was more kinky
less chaps
This question has been on my mind ever since I started reading korean or even chinese bl comics. As far as I can see it, Japan BL tends to have very short chapters and story-wise some of it are kind of farfetched or has abrupt story plot. Korean BL manhwas on the other hand are majority outstanding in terms of it's story. Like I can really see that there's certainly a plot that's going on and you as the reader has to guess about it. It also evokes different kinds of emotions. In a nutsell, I think in a way you could say that majority but not all of the BL manhwas aren't cliche compared to Japan's BL mangas. This is not to say that Japan's bl aren't good since I started reading bl through mangas itself like some of the awesome mangas that I will forever like are Koisuru bokun, Yuuutsu na Asa, Castle mango and many more before growing tired of it and changing to webtoons but the latter itself has a refreshing sense of storyline that gives readers a sense of satisfaction after reading every chapter. At the end though, it depends on your preference. In my case, if I like short and cheesy stories I go to Japanese BLs but I like to read those long and plot with porn stuffs I head over to manhwas.
Why do Japanese bl gets such low ratings compared to bl webtoons? Is it because the sex scenes aren't explicit enough? Idgi