Numerous reports coming out of the Senate Judiciary Committee last week said that former FBI Director James Comey made the decision not to refer Clinton for prosecution long before he even interviewed key witnesses, including Hillary.
I have read several articles which say that Comey did not make this decision. According to numerous reports, Comey was ordered to clear Clinton by Obama, regardless of the evidence or anything she did. That is why Comey wrote his decision so early. Because he already knew that because of Obama, the investigation would make no difference, no matter what they found.