It’s the “Clinton Machine” that protects her. Too many influential people, both domestic and foreign, have tons of money, via contributions to the Clinton Foundation and speaking fees, invested in her becoming President. If she is forced to withdraw, all that money and the potential influence that goes with it goes down the drain. Lots of jobs are involved too - employees and hangers-on of the Clinton Foundation, jobs at non-profits, who have contributed, who expect to receive grants, jobs at for-profit businesses, who have contributed, who expect to receive lucrative contracts, etc.
A lot of money and influence is at play here, that wasn’t available to poor old Petraeus.
She probably still has crucial FBI files on a lot of folks too.
Hillary has the same lawyer as Petraeus, FWIW.
Bill doesn't look too happy here.