The Clintons were/are extremely adept at blackmail and bending the system to suit their needs.
One of their first misdeeds in office was to get ahold of the 500+ FBI files on all sorts of people, friends and foe. These files contain raw data: facts, heresay, lies, innuendo, whatever, and would be useful for manipulating people and the system.
They also did a wholesale replacement of judges with their own people. With these two bases covered, they've seemingly had a fairly tight grip. These are the same tactics used by organized crime families, which is essentially what the Clintons are, IMHO.
Blackmail works both ways, however. With someone as wreckless as Clinton, someone always ready to accept a campaign contribution and with a history of drug use and sex abuse, anyone with the proper dirt or the right amount of cash could get anything they wanted, from military and/or technological secrets to pardons for convictions. This is why his impeachment trial was more than "just about sex", as well as why it didn't go anywhere.
The Clintons and co. are an evil bunch. Absolutely evil! Moreover, they are unafraid. And why shouldn't they be?