Okay, look, there's no way to get around this: Niosi's story was not one incident. It was apparently just the latest in a pattern of behavior spanning YEARS. This includes emotional, physical, and other types of abuse, even coercing fans into certain acts I will not get into. It's GROSS. There's not just one person coming forward, there are several. It is BAD, as in just a bit shy of Vic Mignogna bad. He's also been accused of breaking NDAs when it comes to roles, which is a HUGE taboo in the entertainment industry.
And even aside from the moral reason to get rid of him, there's just the PR. Japanese companies are VERY sensitive to stuff like this. For instance, the Yakuza spinoff Judgment had a HUGE scandal concerning Pierre Taki, the actor of one of the characters as Taki had been caught with cocaine. They recast the character not only in terms of voice, but completely changed his appearance (the character was modeled after Taki). And considering Nintendo's wholesome image there is no way they want to have "Cast an abuser" hanging over their heads. Sometimes these things are questionable, in this case it's not. They made the right call.
And I think it's safe to say we not talk about Niosi for the time being. It's just a mess to do so, though I will say we should believe the people who came forward.