They're just too solid. No one in kpop ever created a group as solid as them. Blackpink has both huge group and individual popularity, in Korea and internationally. All of them are well-known among the general public, and their individual fanbases are just crazy. All four of them have huge individual popularity which has never happened to any group before. All of them are the most followed Korean artists in IG, while boy groups have more sales than them. Whenever they go, no matter which member, they will make the headlines; it will trend everywhere, and they will overshadow everyone else in social media, even popular Western artists. In other groups, even the popular one, only one or two members will make huge splash like that.
They're really one in a million kpop group that people can break their achievements, but no one will come close to their branding. Having a huge fandom is nothing special anymore now so that's why they stand out so much. The greatest thing about Blackpink is that they have both the general public and a huge fandom, so all their members' names are well known. Even many non kpop fans can easily name and recognize all of them. And they did this with really minimum promotion as a group.