I think it's much more likely that the amplification of criticism and outrage was catalyzed by her high-visibility public image stemming from the KP trial. She came out looking (IMO) like a vindictive, petty, and greedy person. Whether that's true or not, I suspect that image was then projected onto her role as Reddit's CEO. The
kind of insults she got were absolutely driven by some of the most vile and reprehensible expressions of sexism, but I think it was more that Pao was an unsympathetic
person who made an easy target for sexists, than that some latent sexism caused otherwise-normal reddit users to turn against her.
I don't think she was responsible for nearly so much of the stuff Reddit reacted negatively to over the course of her tenure as some would think, but I think the primary blame for that perception lies with Reddit's leadership as a whole and their astounding lack of communication to their audience. They knew that Pao had been the subject of a high-visibility lawsuit heavily steeped in social justice implications, which she rather badly lost - it doesn't take a PR genius to think that if you start introducing sweeping social justice-driven changes to your site while she's in office as CEO, people are going to presume that she's the one driving them. That could have been trivially defused by saying "This was a decision made by our board" or "This initiative is something we've been working on for the past 3 years", rather than just sitting by and letting the bogeyman grow and grow.
As another example, as best I can tell, Ohanin let Pao take all the heat for Victoria Taylor's firing, and then clarified that he was the one who made the decision to terminate her only after Pao had resigned. A huge amount of unrest could have been deflected off of Pao if Ohanin had said "Hey, I'm the one that made this decision", but that wasn't said (if I'm wrong, please let me know; the first reference I saw to this admission was timestamped around ~1h ago). In fact, reddit's leadership as a whole was extremely wishy-washy and vague about the whole thing, despite the fact that it upset the volunteer base that makes reddit usable enough to incite mini-revolt.
Leaping to claims of sexism seems lazy and just a little-too-convenient for me. I think that if her husband had been in the CEO role and the same things had happened, given his PR image problems, you'd have seen the same magnitude of criticism and outrage (but then, of course, people would level claims of racism as the cause, which I think would have been equally as wrong).