I realized it's 2 things. One, the people behind them especially songwriters, producers, musicians doing a lot of the backend work. Do not stay with them or go into different parts of their career. When artist don't have so much control over the creative process they do not have a natural growth in their sound which causes core fans to leave. Two, label support - this has alot to do with pt1, if their labels aren't pushing them to several avenues they are more likely not to have a long lasting career. They also have limited black women and the influence they leave behind, which I solely blame on artist using tons of writers who aren't congruent on overall growth for said artist. Beyonce is a perfect example of having ton of ghost writers in her past, but the music that really hits for her shows growth, evolution from her older self in a way.
With many of these singers their social platforms interest is very low. You'll barely learn anything about any of them online. Too much of their careers are built off the hands of other folks. So fans don't naturally gravitate towards them for long fan bases.
When you go back to many rappers history you see growth, new developments in their style, channeling new sounds without sounding not original. We do not see those same elements with female entertainers because often they are not in the room holding control of the creative process. It's why we see Future writing for beyonce and rihanna. Why Nicki career without Safree is going down because it's much more than being a performer.