For me, it's often happened when a group takes a sudden turn before they're able to establish their identity properly (the debut + the first two comebacks for me). Unless I'm really invested in them from their debut, or it's made clear that each song will differ, then I'm not that eager to stick around if they change all of a sudden. Like others have mentioned too, it also depends on how frequently they release content, music and otherwise.
Example: I was really into Weeekly when they first debuted and their subsequent hits, but then they went on that hiatus and came back with Ven Para, which was such a departure. It made the wait bittersweet for me instead of rewarding.
Opposite example: I was into GFriend from their debut. They had multiple songs that resonated with me and made me think of them. Then they came back with Fingertip, which was not my jam, but I stuck around because of frequently they came back and kept doing so because they went back to what they were good at.
I'm not against groups experimenting, but it can often alienate new fans if they do it while they're still establishing themselves and depart from what had been working for them for no other reason than trends. 
