Explain why Hillary Clinton's security clearance has not been revoked

There is a strong belief among the population that Mrs. Clinton received special treatment in the matter of her mishandling of classified material.
Most people who have held a security clearance believe that they would receive much harsher treatment for similar violations of policy.
Even in cases where legal action is not taken, administrative action including the loss of security clearance is very typical for violations of security protocol.
Please explain why Mrs. Clinton is still allowed access to classified material, and what steps are in place to prevent her from mishandling classified material in the future.