Honestly I think the reason why Bayonetta got in as being #1 Worldwide despite being top 5 in the US was because either:
A. Some characters in Top 5 worldwide were put on the back burner for being either cut Brawl or Melee vets.
B. Some were straight up not negotiable to the point where it would have been not worth Sakurai's time trying to get them in (i.e having less artistic license than Cloud in terms of fitting them into the Smash universe, or with things like stages and music, or Sakurai or the other company straight up just didn't want their character to be represented in smash).
C. Corporate shenanigans (i.e Konami and what's happened with them).
D. OR the fact that Bayo got first in Europe and top 5 in US was something only she managed to do (i.e the top 5 characters in Europe and the US ballot were not the same with the exception of Bayonetta being first in Europe and 5th/4th in the US).
I dunno, at this point I'm pointlessly speculating about something we'll probably never find anything out about anyway lol