Essentially, this all began because Zoe Quinn's boyfriend outed her as a cheater, apparently she slept with 5 guys, some of them (or only one of them?) being members of the press. This blew up as people jumped to the conclusion that that she slept with them for positive press (which has since been proven false). On top of that there's accusations of her abusing the youtube DMCA system to take down negative videos as well as interfering in some way with a game jam in order to promote her own, with someone claiming they were doxxed by her (this is all, as of yet, unproven). On top of that, there's claims she faked the raid that happened to her in order to garner attention (again, unproven).
As for Phil Fish's role, he and others have been defending her since the beginning, but things escalated when he and some other dudes started harassing another guy who claimed he was sexually harassed by Zoe Quinn. Add to that what seems to be censoring since a 25,000 comment thread on got completely nuked (which even upset me, until I knew why) and people got really riled up. Some people claimed a mod over at the r/gaming subreddit was in contact with Quinn and accusations of them working together or him being "corrupted" started springing up (and they are still ongoing).
Essentially, a lot of heresay, a lot of accusations, a lot baseless crap being thrown by both sides that's making the gaming community (devs, press and gamers) all look like children slinging mud at each other. No one is the innocent victim in any of this, both sides seem pretty bad, though again, the whole Phil thing was just too much, even if he is a terrible person.