So here's some of the theories
1)"Pledis sucks". Yes, Pledis is not a good company but listen. They never did short cuts with pristin. While nayoung and kyulkyung were in pristin, they were giving us pre-debut contents from other girls. There are vocal covers, dance covers and heck, the 8 girls who did not make it to iou even has a mv called "we". If you look at Pristin's debut and the only one comeback, the mv was well-produced, the songs are really good. They clearly put effort into making pristin big. Also, they promoted pristin well at least imo. That's why i disagree when people say pledis delibrately sabotaged pristin. If they were trying to sabotage pristin, why would they put money and effort in all of these things?
2)"It's because of the kyla scandle." No, i don't think so. Pristin was relatively doing well when they were promoting but they were never big enough to disband just because of one chubby member + i dont think kyla scandle was even that big tbh. Also why would you disband a whole group just because of one member? I don't hate kyla. She is a kind person and no one should be treated unfairly just because of their appearence. But from a bussiness standpoint, if one member is "dragging down" the group's image, what would you do? You will kick out that member from the group, right? No matter how dumb pledis is, i still don't like they will disband a whole group just because of one member.
3)"Pledis gave up because pristin wasn't doing well." Again, they were doing quite okay. Nowhere near twice or blackpink but they were doing well for a newly debuted gg. Pristin has the highest album sales than all of 2017 ggs. Clearly, they were doing well.
So, what really happened to pristin? I don't know and i will never know.
Hopefully we will get to know the truth one day. But it is possible ?
