I find it strange as well honestly, but what can you do ¯\_(ツ)_/¯. Different tastes for different people and some people find attachment to characters they grew up with, and in some cases is just that a few people also like to keep the series a bit more Nintendo focused or have some really strange checklists about what type of characters they want to join Smash.
A lot of the times it is also a sense of community and involvement with a character that is popular with the community in general. Plus some other times is just that people get interested in some of these franchises by seeing them praised by personalities they like. Which can be good when it leads to people discover a new series (a few have been saved from being forgotten) and bad when it leads to bandwagoning in opinions of games people haven't tried. In the worst cases, a few great games can be seen as overrated and dismissed which is something that sadly happens a lot with FFVII.
It it difficult to say as well given that people forget that Sakurai is from another generation, country and culture that is quite different from most people browsing Smashboards or the community in general. So his vision of what characters are important or what characters he would like to see in drastically changes a lot. One point that
osby
brought in another thread is that people like to downplay on Erdrick a lot since they don't know him but propose characters that are probably equally or more obscure to the general public which is hilarious.
When you put it into perspective, nor Joker nor Bayo come from relatively big franchises (Ultimate pretty much outsold the Persona subseries and Bayonetta series already) but they are good additions nonetheless and people should feel more confident regarding some of the smaller series chances. At the same time, people shouldn't also look into the community choices as 100% guaranteed considering polls can be deceptive (I feel that the characters and series added in Ultimate had goo standings in the actual ballot).
There are quite a lot of inconic franchises not only from Japan but from the West that sadly don't get enough love like: Dig Dug, Resident Evil in general, Tomb Raider (which was a cultural phenomenon back in the 90s and still continues), Gordon Freeman, Crash and Spyro, Arthur from Ghosts and Goblins, Monster Hunter, Ezio or AC in general, SNK in general, Dark Souls, and I can go on and on and on. I hope one day people can speculate more about these series in the context of Smash.