“Guys I want to read green arrow but I’ve got to read Shazam first who could’ve known” like this is not the reason.
People are throwing out lots of reasons for manga's dominance, most of them are probably true to some degree. The biggest one for me is that you don't have to read Naruto to start Demon Slayer. One Piece and Akane-banashi aren't the same universe. Etc.