I think is because their audience is mostly teensRecently I am seeing one crazy thing..Newly released kpop mvs are always in (almost)every country's youtube trending..Is kpop that superduper popular all over the world or money is behind this yt trending game?!! Exmple- In my country (India), 90% -95% people don't care about kpop shit, but new kpop mvs (from famous group like Bts.s , BlackPenk, EKxo and now SuperMM) are always in trending list..How???!!! Explain me ..I am just sick of this kpop..This disgusting thing is everywhere..People are being forced to love this nonsense..those bangtonn boys and their trashhit company always love to enter their noses in every country..
I see a lot of random youtubers trending in my country too (no idea who they are).....but they are popular with the teen crowd so they trend
Most kpop fans watch those MV on repeat and that's why they trend on Youtube and also Twitter (there could be money involved to exagerate numbers too)
But just like you said, outside of social media nobody cares about kpop where I live, it's not mainstream music here