The thing is I don't think Smash will help her popularity much.
Bayonetta got in due to a vote, apparently doing really well. Her game sales don't seem to add up with this though.
The only two ways I see that explain how this happened are:
A) Votes for more popular and well-known characters were just so spread out - 2 people wanted both K. Rool and Shovel Knight, for example, but one voted K.Rool only and the other voted Shovel Knight. On top of this, the characters that did beat her just weren't negotiable.
B) This isn't a stab at her character, I like Bayonetta - but I honestly think there was a large portion of people that voted with their unmentionables. It's no secret that Bayonetta is popular largely for her sex appeal. There may be more to her than that, but you don't know that if you haven't played the game/researched it and a lot of people do just kinda ogle her and not play her game. Especially when there are official promotions involving Playboy models dressing up as her, nude shots and everything. There may be people who don't play a lot of video games but know Bayonetta through the Playboy promotion and well...yeah. I mean it's not like the ballot had a restriction of only allowing you to vote on characters you've played the games of. Hell, one of my best friends voted for Bayonetta (and literally screamed when the moon came up in the trailer), and he hadn't played her games. He didn't even own them when he voted (he bought them a few months ago though and started the first game today). Now, my friend didn't vote for her based on the sex appeal, he just liked the look of the game and thought it'd be fun to have a character play like that in Smash. But there are plenty of people who could have voted for her due to pure sex appeal. That explains the dissonance of her being a "popular character who's games actually don't sell well at all".
True the sales don't make sense but I think it's because she is sort of a cult like popularity character.
Yeah she focuses on sex appeal, but she has has a good persona/character. People like her dialogue because it's funny. The games aren't hated, it's basically like the Wonderful 101, amazing game, it just somehow bombed. I own Bayonneta 1 and 2,( well my brother brought it to try it out). The games good and fun, but super difficult, which turns some people away imo. However her likeable character, and fanbase, I believe had a bigger role in promoting her in the ballot. While sure guys couldn't be thinking with the wrong head,( please don't infarct me), I really don't see that being a major factor, maybe a few votes, but I don't think she is known enough in that way to promote such results that way.
This is where the other 4 charcters come into play imo. My guess for the Top 5
1-3) I'd be willing to bet that these first 3 in any order were topped ranked:
Banjo, Goku( or shrek), and K rool. Goku and Shrek are out for obvious reasons, Banjo might have been harder to negotiate, or they might not have wanted to add an "outdated" character based on Sakurai's interview on FE, that Sourcegaming did a few days beforehand. I believe this was the same reason for no K rool.
As for Number 4? Inklings would be my guess. As for why no inklings, it's probably because of the difficulty in making them imo.
I would even wager an unrealistic 3rd party or even character in general( could be so many different ones, that I don't know who). could have been up there as well. I think the top 10 had mixed results across the nation, but Bayonneta was there for each region, and was the most viable option they could do. I imagine there were several other big characters, but unforeeseen reasons led to them being undecided.
Of course that is all speculation on my end and doesn't explain how Bayonneta got it, but i thought I'd share it.
In conclusion, I think it's more her character( in both physical and non physical ways) helped push her higher then most expected and led to her inclusion. Also while many seem to disagree, I honestly could easily see Bayonneta being popular with casual gamers. They see the boxart, a discounted game, and a fun genre, and go " hey this looks like a fun game to play! I'll try it!" and thus her name gets out there one way or another and more people enjoy her, as well. Because of this and her core fanbase, votes pour in that make her highly ranked in the ballot. But again that's just
a Theory! A Game Theory speculation.