Why did ROSÉ's solo have more success than the rest of her members?
I think it's mainly due to her artistic direction. Out of all her members, she is the one who really has a vision about what she wanted to do and stuck to it. Her songs have a true message that is relatable unlike the rest of her members were they mostly write songs that are self-gratifying. There's no sort of relatability to it cuz they sing about the same star luxury life and that's not a bad thing but how many people can relate to being able to afford the luxury life? Heck people can even barely afford the average life. There is the exception of Jisoo but "Flower" seemed kind of generic. It's like something the average vocal-focused soloist would release so I think Flower only really went viral because Jisoo was the singer. If it was any other singer, it would not go anywhere.
Now I could go into detail on Mantra and Rockstar but I don't want any other BLINKS to feel attacked.
This is solely my opinion so please take no offense to it because I'm not trying to discredit any of the members.
I'm just sharing what I think is the case here but of course I may be wrong and you are welcome to disagree.