(assuming you're serious?)
1) Victoria, the admin who interfaces celebrities and /r/IAmA, was abruptly dismissed. No cause given, which grew a lot of conspiracy theories, but that's obviously standard practice when you fire an employee.
2) /r/IAmA mods find out when a PR rep reaches out to them after showing up at reddit offices and finding out their appointment with Victoria was canceled. Mods don't know how to get in contact with other people who are supposed to appear that day. They take the subreddit private, with a short message about having to figure the situation out.
3) Reddit uproar starts. /r/OutOfTheLoop post asks why /r/IAmA is closed, an /r/IAmA mod explains, people get upset about Victoria leaving. Separately (in my opinion) — or centrally (in tptacek's)— the hate subreddits from prior incidents like /r/FatPeopleHate deletion and GamerGate kick into high gear.
4) Other subreddits start going private in solidarity. This spreads until over 100 have shut down, pledging a 24 hour blackout. I think the petition starts around this time. /r/all is basically just this drama.
5) General shenanigans. Flaming, offensive content, etc. /u/kn0thing (Alexis Ohanian) posts a flippant comment in the heat of the moment, starts getting flamed too. Mostly though, he says "Not going to talk about Victoria. Chill, we're gonna get this /r/IAmA stuff figured out," on behalf of the admins (reddit staff).
6) /r/IAmA comes back up, says they're independent from the admins and are going to run things themselves. Ellen Pao talks to news media, posts eventually but gets downvoted to 0 - all her comments were thousands negative and had lots of angry/offensive replies. (Later we learn many positive things were said to her too.)
7) A week passes, mostly dying down. Petition gets more signatures, ultimately reaching >100k I think. Eventually they post an apology, to mixed reactions.
8) Sam Altman posts that Pao resigned, but includes a reproach of the behavior exhibited in the prior week. Seems to get positive reactions from both sides – people welcomed a return to civility and also Ellen's departure. People suddenly start realizing that the horrible things she's been doing to reddit might be because of reason and/or outside pressure, not because she hates freedom and happiness.
9) People start using this incident to complain about internet behavior more generally.