Chrono is the main character, but I'm really not sure that means a whole lot since I don't think his reception would be as big as Geno's. Technically, Rosalina and Meta Knight are supporting characters, but I don't think that was really a major detractor for them. Plus, even if DKC sold lots more than SMRPG, I think Geno seems to have closely tailed K. Rool in popularity, and I'm unsure if the whole Kremling crew was significantly more popular outside of Smash than Geno. It's not an exact science, but I think the scenarios are kinda similar.
Sakurai thinking a character makes sense goes a long way - Corrin's reactions where subpar for sure, but they made it since the moveset was interesting and Fates was big news. I definitely think fan clamor and personal bias could get Geno in during a Smash Direct.