Going to the police around sexual harassment has a poor track record of going anywhere, even with witnesses. Most of the time it winds up around competing accusations. Evidence is often scarce, and with charismatic folks involved, people may not realize the extent they've been manipulated until later. Abusers often target people who are not in a position to speak up, where their career could be at risk. Conventions are also a giant issue - doing all of this hundreds of miles distant even further reduces the odds of success, and ratchets up the stress. And, of course, the stress of spending the next few years being literally forced to deal with your abuser by the legal system.
That's before you get into things like real cases where police gaslighted a rape victim into recanting, prosecuted them for reporting the rape, and only come around once they catch the rapist who kept the physical evidence of the rape exactly as reported. Or the public attacks against the credibility of people who report to police, have witnesses, photographic and video evidence and pursue a restraining order, exactly as people tell them to. Or people assume you're lying because you don't react the way they expect you to (hint: many rape victims do not weep or rage - mostly, they dissaociate, and come across as calm and a little cold, because on many levels, they're avoiding emotional connection to the events as a coping mechanism. But guess what behavior is extremely likely to make people doubt your accusation?).
So people wind up not reporting, and maybe convince themselves it was a one time thing, or maybe she played too big a role in it, and he's too important... then someone else mentions something. And someone else. And a fourth person. And it snowballs, and you wind up in a situation where none of the victims can make effective claims in court, but something is obviously wrong. Remaining silent means that others are going to go into interactions with this person unprepared. So, people say something. Eventually, enough people, with enough credibility, step forward. Some stuff that other members of the board have seen goes from odd to seriously concerning, so they step down. Some of them, like you, don't want to see action without a legal conviction, so they step down. who knows what the rest thinks, but good odds they just decide to give the org a fresh start.