Although applicants are mainly women, there are many men still making the decisions, especially in the upper echelons. And even those who suffer the effect of implicit biases can have implicit biases themselves. You have too much faith in the psych world-- we are still susceptible to our implicit bias, just as anyone else in any other profession. Sometimes even more so, since we think have a handle on it, which may be the situation in your case. Hopefully we all can learn from this situation!
But yeah, never spend too much $$$$$ on interview clothes, totally not worth it in the long run.