The more I hear about the corporate politics at Reddit, the more I realize it's an impossible ship to steer. I don't think Ellen Pao realized the level of communication and transparency that online communities like Reddit demand (or that anyone with "power" over such communities will have complete transparency forced upon them); but at the same time I don't think she was the driving force behind many of the changes carried out under her watch. She just wasn't there long enough. But the job is kind of a damned if you do, damned if you don't situation. It's impossible to satisfy the users screaming "free speech at all costs!" when the board is demanding you get rid of the trolls whose main reason for trolling is usually some variation of "because we have free speech".
And she didn't leave to pursue other interests; she was forced out for reasons not made public. She certainly was unpopular on Reddit, though it's hard to know how much of the Reddit zeitgeist/groupthink/circlejerk is manufactured by small groups of influential users. I think the board decided she had to go simply because they didn't want their user base leaving en masse, and getting rid of Ellen was the only thing that would satisfy the user base (or at least the "power user" base). From what I've read, the board is anxious to monetize the platform in some way, and it's hard to monetize a platform where trolling and harassment are as commonplace as they are on Reddit.
And to some extent, I'd say that Reddit itself actively resists commercialization. One of the greatest benefits of Reddit as a user is that the algorithm is relatively simple to understand: users upvote and downvote, and while it's easy to see how to game that system, it also allows for the possibility that content will rise to the surface organically (even if a lot of the content is manufactured and upvoted via click farms). You don't get that if you're restricting the content, and I think trying to commercialize it would destroy the feeling of chaos that makes it so successful.