Who was in charge?

Can anyone, anywhere explain why the DNC would not turn over a compromised email server to find out who was in fact responsible for the hack?  Jeh Johnson had no answers in court today as to why the DNC refused the offer to help. I guess my question is if this was a matter of national security and election integrity (as Democrats now claim it to be) Why were they given an option to deny that help? Who was running the FBI then? Who was President? WHO WAS IN CHARGE???