I feel like many here have the wrong attitude.
The halacha generally is that until allegations are confirmed by two witnesses, it's "Chashdaihu V'kabdeihu" - suspect but respect. You are not allowed to believe the allegations, but you must put safeguards into place to protect potential victims.
Today, the man is no longer alive, and even if all allegations are true, he can no longer harm anyone. Thus, until we have a clear psak from a reputable bais din, there is no reason to believe any of the allegation. Yes, I know some will be quick to say that the victims will suffer if nobody believes them, but 2 points - 1) who said that's a reason to permit being mekabel lashon harah, and 2) I'm pretty confident that none of the alleged victims read DDF.
That being the case, even if Yonason Schwarz's voice note is suspect, and we would not be inclined to believe it on a standard matter, here we should cling to the belief that the man was innocent. All the talk about 'dozens of victims' is not coming from sources we would trust if they were the ones telling us not to eat from our favorite restaurant. So why are we being so quick to condemn a man who can no longer do any harm?