IMO, YG is at the heart of this and this is besides any "favoritism" displayed.
A group of charismatic and talented girls debuted to much fanfare in 2016. Over their five years though, group content has been kept at a bare minimum and thus people interested in the group have had to search elsewhere to get their fill of their faves. It led these people to their solo activities, of which all the members of BP now have more of than group content. This then led to some very focused exposure to the members on their own. Even though all members got exposure through various brand endorsements/CFs, it was very easy to follow only one and develop as a stan through that. And then congrats, perfect breeding ground for solos.
On top of this, Blinks are basically getting crumbs. They are hangry and it shows.
This is spot on. Look at BTS, the focus is always on the group first! They are very much a unit. Now, BP all get on really well, but YG promotes them separately so often that some people wrongly assume they don't. Jennie and Lisa in particular are usually seen together off cam, on they are rarely put together. I feel YG has made things so much worse.
The perfect way would be them having a full album, then having one solo per year. But the way YG did everything was backwards. Lisa's shitty promo period was yet another disappointment.