I'm glad redditors have started to piece together all of this. Here's the only thing you're missing:
It travels upstream, except when it comes from the CEO's boss.
Alexis wasn't some employee reporting to Pao, he was the Executive Chairman of the Board, i.e. Pao's boss. He had different ideas for AMAs, he didn't like Victoria's role, and decided to fire her. Pao wasn't able to do anything about it. In this case it shouldn't have traveled upstream to her, it came from above her.
Then when the hate-train started up against Pao, Alexis should have been out front and center saying very clearly "Ellen Pao did not make this decision, I did." Instead, he just sat back and let her take the heat. That's a stunning lack of leadership and an incredibly shitty thing to do.
I actually asked that he be on the board when I joined; I used to respect Alexis Ohanian. After this, not quite so much.