The Clintons have too much dirt on them and they have made too many enemies among "their own". They have used and abused and thrown away too many of their own. That and her Marxist rhetoric. Businesses, the medical profession, et. al. will go against her.
Clintons have a lot of dirt on many people, but Bill has been out of office for over 6 years now. Their files are getting old and they can't order the CIA and FBI to give them whatever they want anymore.
There is alot of new blood that they can't blackmail so easily.