I think this is the kpop fan mentality. They think fans will necessarily stan another artist as soon as the one they like slows down or a new face appears. They think people have to do it and they can't accept that not everyone works like that.
When this is discussed a lot of people imply that BTS owe a really big part of their success to those 1D fans when it's not true. Copying mechanisms I guess.
I understand that it can and does happen, but from what I've seen in kpop, the majority part of that "inheritance" is younger sibling groups inheriting fans from their older sibling groups. A lot of people use that line for other 3rd gen groups too (whether or not its true). But BTS never had older siblings to inherit from. Fans of a western English speaking boyband weren't just suddenly going to transfer to stanning a foreign Kpop Idol group en-masse.