Like it was a thing people said a lot -- "we don't know where she stands" -- but we did. People kept saying she didn't answer questions -- she answered questions. The impression that she wasn't communicating persisted. I've seen this happen to many smart, capable politicians (though mostly Canadians examples coming to mind) -- they just can't duck a impression of what is going on even though it's not what's really going on.
But also, I think a lot of people just need a reason to say that isn't "I don't want to vote for a woman."