Not surprised very few people were aware of this fact, and the fact that he was struggling and had a outburst just lends more credibility to his claim, honestly.
There's a disconnect you make when you are working with people in a position of power over you, you don't want to believe the worst of them, and so you brush off minor red flags as "just jokes", and convince yourself "such and such is actually a good person, just makes some awkward jokes sometimes" because you don't want to consider the possibility that they aren't jokes, as a self defense mechanism. You don't want to feel unsafe, and if nothing solid or concrete happened to you personally, it's easier to dismiss it as just that.
The fact a few people in the company do believe that he was harassed means that maybe people are starting to piece together that "oh, maybe that wasn't just a joke" and it's a slow dawning realization that hey, this might actually be a thing.
I will always believe someone who claims they have been sexually harassed/assaulted until it is proven they weren't, because so many times these claims aren't taken seriously and ignored, when it really was a serious issue, just the public would rather sweep it under the rug, rather than address the elephant in the room.
I have known a handful of people in office environments and other work environments that have been sexually harassed by their bosses, and when I asked them if everything was okay, they'd just tell me, "oh it's fine, s/he's not being serious!" because they didn't want to rock the boat and possibly lose their job, or face the reality that things were not in fact okay, and that something horrible was being done to them. (fortunately they no longer work in those places and are in much healthier environments, but it was so fucking painful to watch people you care about put up with this BS for years)
Also, I fully believe that many employees may not have been aware of the fact at all -- that's how many predators get away with it, they put on a shining beacon personality, and come off as charismatic and charming as to cast off all suspicion. If allegations come to light, then everyone will say, "Oh but s/he seemed so nice! I could never imagine them doing that!" because it makes it harder to believe they could be capable of doing anything heinous, and if they were particularly gross, they could make up lies and cast further suspicion and doubt on their victims, causing the victim themselves to doubt whether what they experienced was actually harassment/assault, or if it was something they imagined in their own minds. The victim might think, "maybe it was my fault, maybe I lead them on, maybe I interpreted this wrong, maybe this maybe that"
It's not a fun place to be in, and it's 100% not something easy to talk about. I really hope something concrete comes to light to remove all doubt from the situation, but things like this are incredibly hard to prove unless someone is a cartoonish creep with 0 awareness, but you don't really get into positions of power by not being a bit socially aware and charismatic at the very least. It's murky waters, because we don't know the details of the situation or what the harassment entailed, and the victim themselves may be second guessing themselves at this point, especially with how this all blew up. Were it me, I'd stay silent too, because when all you want to do is get something off your chest and then it turns into a huge deal, that's terrifying.
Ballard may have firmly believed he was harassed in the past, but with all these people bringing arguments out against him, he might start thinking, "Maybe it really was just the intense work hours, maybe it really was just this, maybe it really was just that" and that will make it even harder to discuss as you start to internalize that it was something YOU did wrong, rather than the abuser. That YOU are overreacting, and your abuser was in the clear.
That people at the company admit they were unaware, but believe him, speaks volumes. I will fully believe that people were unaware of what was happening, as you can't always know the intimate details of all your coworkers lives, but the fact they believe that something was going on, and that there have been other claims of sexual harassment at ND (at least one I saw) further concretes that something actually did happen, especially because, there is nothing for Ballard to gain by lying about something like this.
I just hope the dude is okay, this is already a very heavy thing to have to deal with on your own, and then having the scrutiny of the internet laser focused on you and dissecting your entire life to fish out details and prove you right or wrong is incredibly intense. People who want to believe he's a liar will be digging through his past and looking for excuses and things to discredit him, while people who want to believe he was telling the truth can pull out innocuous things and take things out of context that aren't related to prove "oh gosh look at the way he typed here, clearly something was wrong!"
I'll just say, props to the dude for having the courage to come out and say this stuff, it's so fucking difficult to actually admit, much less talk about, especially about a company held in such high regard as ND, and damn I feel bad that this blew up the way it did. He probably intended for that tweet to be cathartic, to get it off his chest and feel a little bit better about something horrible he endured, and then it turned into a full on investigation of ND, and I can't imagine how that feels.