Well BWD popularity began simply because he was a notable character in the current game, which is all it really took before he started recurring. People had a Kirby newcomer slot they wanted to fill, but there was no obvious next in line, so it'd just shift from the current character to the current character, despite that not being how Kirby worked. Before BWD it was Prince Fluff, before him it was Daroach. Gooey would show up time to time.
Ah, yes, I remember hearing about guys like Fluff and Daroach. Man, that feels like a long time ago...probably because it was.
And yeah Dee being the current flavor was definitely a lot of it. And that was also part of why I felt some fans made too much of his RtDL appearance; it was only one game and there was no guarantee it was gonna be the start of a sustained breakout. Even if he kept on appearing as the P4 character, I still didn't think that was necessarily gonna be enough role-importance-wise. He was
at best the fourth most important in RtDL, probably even fifth if you include Magolor. Of course, Magolor was/is popular, too, though didn't end up recurring quite like Dee and (for quite a while) wasn't in a playable role.
I hate to be that one, but I may need some convincing here. If not for RtDL, what other game has Bandana Dee been important enough in to justify an inclusion? To my knowledge, Forgotten Land was the only other game that didn't give him a passive role.
The way I see it right now, people have been giving a lot of credence to him being absolutely next in line. But this is probably the exact trap that kills healthy speculation.
Well, at this point he has several playable and assisting roles, the height of them coming with being the "player 2" of FL. Sure, you can argue that a lot of his roles aren't all that important, or at least not "starring" roles. I wouldn't really argue with that. But he does appear more and is playable more than any other notable Kirby candidates, in addition to carrying the most popularity as of now, which is kind of the basis for saying he's next in line.
I do think at this point Dee is the strongest overall candidate for a Kirby newcomer but that doesn't mean there aren't other picks I'd like to ultimately see, too.