Its bcs many manhuas we often see are actually adaptations of popular web novels. Publishers and studios pick novels that already have a strong reader base, meaning they’re more likely to succeed as manhuas. This is why you see so many similar tropes, those genres and character types are what most audiences enjoy. If a novel featuring a modern-world system with a black-haired, overpowered MC gains popularity, it’s a no-brainer for publishers to serialize it into a manhua.
And let’s be real, the whole 'black-haired nonchalant MC' archetype has been around forever in anime, manga, and novels. Sung Jin-Woo just made it more mainstream. Characters like Fang Yuan from Reverend Insanity, Gu Changge from I Am the Fated Villain, and Ye Xiu from The King’s Avatar, Even Cadis Etrama Di Raizel from Noblesse fits this mold of the cold, calculating, or reserved MC style way before Sung Jin-Woo’s rise especially in chinese manhuas where most of them are 'supposedly' all-rounders.
P.S. Sorry for the rant it's just that people usually almost compare most serialized manhuas and manhwas that were adapted from webnovels to Solo Leveling, but Solo Leveling in fact due to its immense popularity as a novel led to a manhwa adaptation, which began its serialization.
Therefore, it's more accurate to state that "Solo Leveling" was selected for serialization as a manhwa due to its with popularity and its existing strong reader base.#－.－)
Again sorry for the rant just had to get it off my chest ( Q^Q)
it wasn't that long of a read it's okay (^^) but i jusf wanted to express my opinion that mcs aren't really original these days
ik this is only the first chapter but can we stop with the generic black haired mc who acts nonchalant, it just reminds me of jinwoo and I think they know what they're doing