The purpose is that she was a disaster of a candidate and that they don’t want her. They are warning her, through the revealing of salacious, but not illegal, activities, that the DNC is willing to release information about her acts of criminality and murder if she does stop trying to run for President.
That, and perhaps wanting to live another day.
To sell copies and make money; even at the expense of turning on her own, but I quite happy with it in that is further exposes the Democrat Organized Crime Syndicate. Not to mention, she may believe someone is going to jail, and wants to vindicate herself now.
Meanwhile, bear in mind, that many within the DNC regard her as too moderate.