Someone massively popular like Dante barely existed in speculation compared to smaller characters like Phoenix Wright, as a frame of reference. Emphasis was largely Nintendo-centric and we did not have the imagination to envision how the hell someone like Chosen Undead or even Steve would get into Smash Bros in 2014. That's Ultimate brain, not Smash 4 brain. We could barely process that Cloud was in the game.
I think something else you’re missing is that fan demand doesn’t exactly correlate one to one to series sales. I feel like there’s just a lot of overlap between Kingdom Hearts and Nintendo/Smash fans as they both feature colorful and upbeat characters that are fun and exciting. His moveset from Kingdom Hearts also just naturally fits a game like Smash well, which helps.
That framing just brings even more disbelief because then why Sora of all characters?
Waluigi, K.Rool, The Belmonts, Inklings, Chrom? Returning vets like Wolf? Even SE like Chrono and Black Mage. Those with actual Nintendo presence, Sora is the most Nintendo-centric pick at the time of Smash 4?
The games that came on Nintendo systems were the smaller niche side games that came to handhelds that even needed previous main entries to gain full context. The popular main numbered games where always on Playstation as an solid exclusive. The KH collections including all games from KH1 to DDD was the recent release at the time of Ballot and it was all Playstation Exclusive. There wasn't any strong connection between the KH and Nintendo at all. Sora was always a PS guy
To this day, we still don't even have a proper collection release on Nintendo systems unlike Playstation.
The King of Phantoms is one brought up sales numbers as a factor which i shot down as factor as it doesn't hold up.
Steve was said to be negotiated 5 years before his reveal which lines up strongly with the ballot. Even in 2015, he was strongly regarded favorite with the Minecraft boom going strong. I argue the connection of Nintendo fanbase and Minecraft greatly aligns much more than Kingdom Hearts. I don't like using fan polls as sources but even those polls Steve usually topped Sora on the charts. No doubt he dominated the ballot.
Theory territory but Bayonetta was probably picked the "ballot winner" at the time because Nintendo couldn't secure Steve in time for Smash 4 DLC so was saved for Ultimate which would explain why Vergeben and his sources picked up the info of Minecraft content coming to Smash but he couldn't pinpoint what because Negotiations took longer than expected even during Ultimate season.
Very likely Steve was going to final major pick ending off Ultimate DLC as true winner when the next pass was still 5 until Sakurai met the Disney VP and retroactively added Sora not a winner but as the unexpected surprise that most would never see coming/would happen finale. Only adding the "ballot" winner spin to drum icing on hype cake.