it's weird seeing adeleine with a nose, huh
Indeed, she looks nice and all, but I think without a nose (like she was before) she would have felt more natural for the Kirby series... but she's fine anyway, it's not the first character to have human-like details (look at Bonkers for example, still being a monkey, he has Popeye human-like arms and wears pants with a belt).
Daroach makes way more sense to headline the series as he is way more prominent then the other two. He's a supporting character in Mass Attack, Shows up in special 20th anniversary artwork (of which only Animal Friends and SuperStar characters appear in) a keychain in Triple Deluxe, two stickers in Planet Robobot (one of which was a special doodle sticker) and a hat in Battle Royale.
This is also a very special appearance for him because it marks the first time he's appeared with a full 3D Model. And they're going all out with his attacks, Ice Beam, Bomb pillar, Triple Star, Animal Attacks EVERY SINGLE MEMBER OF THE SQUEAKS! Now that they have 3D models, I expect to see him a lot more often. It's a big highlight for the character!
Helps his design has very wide appeal similar to Marx. He clearly has a cool design, but it's not over the top and edgy like Dark Meta Knight, in fact as a mouse, it's easy to find him cute. He also has an awesome theme making him very marketable.
And then there's his role in Squeak Squad. While Dark Meta Knight and Adeleine play notable roles in their games. Daroach is essentially the MASCOT of Squeak Squad, not only is he featured on the cover and a lot of artwork. He's even the games LOGO.
Basically, being the front-runner of the wave 2 should have been expected
Also, he's a singular character, he fits nice and easily on the link and tab, Adeleine & Ribbon would be a harder fit.
That's very debatable, both characters were very underused until the implementation of the Dream Friends, and the only point that can be used to compare the relevance of the two characters is the amount of cameos.
Adeleine appeared in 2 keychains and 1 Robobot sticker, in the 25th anniversary artworks appeared multiple times where Daroach appeared only once, and in the 25th anniversary wallpaper (the one that also became a 3DS theme) Adeleine appears and not Daroach.
In addition, Kirby 64 is a way bigger game than Squeak Squad, more important in the series and more popular; and she also had a role in Kirby's Dream Land 3, even if her design was changed.
See, depending on how you watch it, one character is more important than the other, but really, they are in a very similar situation.
Anyway, I don't want to start a character fight, I like Daroach too, but as you said, Daroach alredy recived an hat in Battle Royale, and anyway his reveal didn't make much noise at all, while the announcement of Adeleine made Kirby's Japanese twitter explode.
There is clearly a lot more hype around Adeleine's comeback after 18 years, than the return of Daroach, and I think it would have made more sense to take Adeleine as the front-runner.
You may be right about the fact that Adeleine & Ribbon are two characters and maybe Daroach just fits better in the site's layout (especially when you zoom out the artwork, Ribbon may be hard to see because she's tiny), that's the best explanation I can think of... or maybe they already planned Daroach to be the front-runner way before, and the Adeleine hype was unexpected, so they didn't know at the time when they made the icon... who knows.
I even suspect that Ribbon was not planned to be with Adeleine and they added her last minute because some people complained about it on Twitter, it may even be the reason of the delay (maybe the Squeaks too).