Because she is that evil
Hillary is a symptom of a systemic problem in any large organizations—the sociopaths rise to the top and the most evil sociopaths rise to the very top.
I have seen this in governments, private corporations, non-profit organizations including churches, even local home-owner associations.
Sociopaths are not evil for a reason—they are evil because that is who they are—they crush people with no more concern that scraping bugs off of their windshield to clear the view.