I think what's happening with Kane is that there has been a lot of anger building about a lot of related issues for a long time - a long history of similar allegations not being taken seriously and no real consequences for a lot of athletes in a lot of sports (and a lot of other people in a lot of other industries). Castro was long enough ago, even if it was only a couple years, to benefit from that. People are more aware now than ever about the influence of sexism in our culture and there's been a lot of high-profile shitshows in and out of sports - the visibility of twitter harassment, football's endless stream of disasters, gamergate, just lots of stuff happening that I can't point to any statistics for but do think has been kind of swelling in cultural importance, particularly among People Who Read Shit on the Internet. Folks are angry. They want to see actual consequences for bad behavior that don't require video evidence so heinous that even the NFL can't ignore it.
So when Patrick Kane gets accused of rape during a championship offseason, it's basically a perfect storm. He's incredibly high-profile and he's certainly earned no benefit of the doubt. The accuser went straight to the police and the hospital, which even putting aside the statistical unlikelihood of false accusations, is not the behavior of someone simply looking to extort a payout. For the first month and a half of this disaster, there was no real reason to think this wasn't a case of a star athlete doing something heinous. Patrick Kane seemed like the poster boy for doing something awful but being good enough at hockey to get away with it. So when the league declines to suspend and the team holds a pretty boneheaded press conference and welcomes him back to camp, plenty of people hit their here-we-go-again limit and pushed the big red apoplectic button - fuck all this, they're done. I get it, it's a legitimate response, I've done it myself in other situations that I hit my personal limit on, and the Blackhawks are not owed anybody's allegiance, money or attention. Anyone deciding that this was just another entry in a long list of negligent behavior and that they considered it the last straw is certainly within their rights to do so.
The poke in the eye is, individual cases rarely stick strictly to the expected narrative and are not required to conform to statistics. I absolutely assumed for the first month that the state of NY would eventually get all their ducks in order, there would be charges filed, and at that point he would be suspended and I wouldn't have to look at him anymore. But watching that DA's press conference, with the Brady rule DNA disclosures and the evidence tampering hoax and the uncooperative witnesses and the withdrawing attorney.... I don't know if it's officially ironic that the case everyone finally decides is the Final Straw is the one where there's this much legitimate doubt, but it sure is something. And I think you're right that everyone looking for a better institutional response on sexual assault allegations going all-in on the outrage in this particular case has the potential to blow up in the face of everyone who wants the world to be better. It already is, to some extent, which is just making everything worse.
It's undeniably hypocritical to root for Castro and the Cubs (or the Kings, or the Avs, or pretty much every other team or sports league) while declaring yourself done forever with Kane and the Blackhawks. It's not a mortal sin, though - lots of people are hypocritical about lots of things, all the time. I know I sure am.