Honestly, I think it's a case of Yuehua getting some shiny new toys and not thinking much of the old ones. Both tpst and Yena are selling about 100k albums now while EG sells about 50k, and they managed to double what they are selling in the fraction of time.
That doesn't excuse them dumping EG though. They are still a very popular group with room to grow. I think EG has a lot of casual fan interest (their spotify streams are a lot better than Yena and Tpst), but has trouble converting it into fandom. Still though, with patience and a streamline of good activity going, they can grow. It's really a shame Yuehua doesn't seem to think it's worth it.