I'm finally getting back into Kirby, so I've been studying the lore a lot more. Turns out that Dark Nebula is a form of Dark Matter according to the Japan-exclusive 20th anniversary artbook. So I like to think that high-ranking Dark Matter beings are sent by the leader (Probs Zero) to be the leaders of Dark Matter hordes. For example, Miracle Matter would be in command of the Ripple Star Dark Matter, and maybe Zero tried taking Pop Star by himself. Maybe Zero isnt the leader at all. I was also thinking that maybe Dark Nebula was one of these leaders who managed to get captured in a chest and sent to Dedede in Squeak Squad. Dedede doesn't seem like the kind of guy who would hunt down Dark Matter on his own.
Eh, that's just me rambling
I reread that first fanfic I wrote like a year ago and dang, that was pretty cringeworthy. I still think the prehistory vibe of my second pitch would actually be pretty neat. And of course, lots of Kirby fans always want some kind of connections to Dark Matter in a Kirby game, but that really isn't necessary.