What? But what about Ridley, Simon Belmont (I know I voted for him), Isabelle, Daisy, Chrom, and Dark Samus? Maybe they got many votes too? I am sure Inkling got many votes but I am not counting her. It was obvious Inkling was getting in anyway, ballot or no ballot.
To be clear, Ridley is definitely a "fan demand" character, but he didn't specifically get in because of the ballot. Obviously we don't have the results of the ballot so we can't say for sure, but he was very likely hurt badly on the ballot for already being a stage boss and Sakurai going out of his way to explain why Ridley couldn't be a fighter in Smash 4. This is supported by the exit poll, which has Ridley 15th behind many other first parties like Isaac, Bandana Dee, Paper Mario, and even Krystal. So yes he's popular, but didn't really get added primarily due to the ballot itself.
Simon Belmont is popular and is a gaming icon. But like Ridley, he isn't necessarily due to the ballot. The exit poll has him 28th. Almost surely he wasn't voted on as much as other third parties like Geno, Banjo, Rayman, and Shantae. I've argued in previous posts that Simon is more of a "Sakurai choice" so to speak than a fan pick, though my arguments for that are admittedly a bit less concrete. I will also say that demand for Simon didn't really explode until after the Vergeben leaks and the knowledge that Snake was coming back.
I hesitate to label any Echoes as truly being ballot choices, mostly since they are characters that likely wouldn't be in at all if they weren't easy clones. Daisy is popular among Mario fans but within the Smash fanbase there's no way she placed higher than Waluigi, for example. Dark Samus and Chrom did get some votes on the ballot, but they weren't all that high up according to pretty much all the data we have. And again, I doubt they would've been added without being easy Echoes.
So the short of it is that they pretty much only "used" the ballot when it suited them, whether that be taking the most popular out of the easy clones or citing it whenever it helped them justify an inclusion ("Bayo wun Yurup guyzz"). They also picked a handful of characters that were indeed popular, but Sakurai's knowledge of these characters' popularity would not come primarily from the ballot. So there is an argument that the ballot itself was barely used; the glaring exception is K. Rool, who was likely the winner.
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Timing was also a big issue
Yeah not saying any of these other things weren't issues. Just that I don't think that any of them are the main issue.