When an older group doesn't get proper treatment and a newer group comes around being the company's top priority, there's usually hostility between both groups and their fandoms.
There are several examples of this, like CLC stans and GIDLE stans, for one.
Even Red Velvet got alot of hate from their senior fandoms when they first started out.
However I don't think this is the case for Reveluvs and MYs. If anything I see more Reveluvs supporting and stanning Aespa compared to actively hating and bashing them.
Why?