There's nothing unique about them
Beyonce was a great performer and had great energy on stage. She always carried herself like a star that's been there before, that's the main character (even at the expense of her crew in destiny's child)
Rihanna had that island girl quality going for her
Sza has her own brand of R&B (has a low key, lofi sound kind of)
Chloe should have just made music more similar to what she did when she was still singing with her sister.
Normani had some hits though (Love lies, dancing with a Stranger, motivation)

so I'm not sure what happened there
Also, I mentioned this before: you CAN'T be TOO oversexualized from the start if your music is basic. Otherwise people won't take you seriously