I think when this broke, her connection to Hillary and the Clinton Foundation kept being played. Also during that same week, news broke that Marissa Mayer hid the huge yahoo data breech from users for years and purposefully didn't take ethical actions addresssing known vulnerabilities. These are three of the most powerful self made women all of whom were heavily publicized for years. The anti-Clinton sentiment along with valid criticism against Holmes and Mayer very well could have burgeoned into an anti-women sentiment.

As for the sexism, I felt like it was more of a backlash against the unrelenting positive press Holmes received for years, right or not partly due to her gender. Every time someone commented on why they thought something was wrong with Theranos they were drowned out by voices telling them to stop being sexist and you want her to fail due to her gender. Justified or not, plenty were happy to see her fail after all the praise she had recieved and I am not surprised at all if some of the blowback was sexist.

That being said, the majority of the discussion was anti-Theranos though I do agree with you there were a fair bit of anti-woman backlash though like I said much of it I feel was prompted by the positive praise she received.