To deny that there's a bias towards leaks with "favorable" characters is a bit ridiculous.
This sort of thing has happened throughout Smash history.
DaybreakHorizon
even provided a prime example; Tower of Smash was given spotlight treatment even though the only things it got explicitly right was the return of Onett (an easily predictable retro stage), and was kept alive even after getting not one, not two, but
three consecutive stage names wrong. The third of which, wasn't even in the same ballpark.
Why was it so popular? Because it was a post-3DS release SSB4 leak that said Ridley could still be playable.
It's not even the only example of this happening. Have you heard of Miahstorm? The leak that was popularized after the fall of Gematsu? It wasn't even the only one that said Chrom wasn't playable prior to his disconfirmation, but picked up traction over its direct rival; why? Because it said Ridley and K. Rool were in, whereas its rival said both were "playable in a boss battle mode".
Even the ESRB leak, the one everyone and their mothers are comparing the Grinch leak to, is an example of a leak getting treatment that coincided with the characters it implicated. Most of the community was thoroughly convinced it was fake even though it had much, much more to it than the Grinch leak. It also just so happened to disconfirm
every single remaining community favorite with the sole exception of Shulk.
It's hard to write all of this off as a mere coincidence.