Obama never intervened in the investigation. He gave Comey free reign and so did Lynch who had to recuse herself. Comey-- a conservative Republican--went so hard to get Clinton that he broke FBI rules in appearing before Congress and providing derogatory evidence against Clinton as if she were guilty instead of having been cleared by the FBI investigation-- this is what was stated in the FBI memo sent to Trump to support Comey's being fired. The memo included a statement that Comey provided derogatory evidence to congress when he should not have even appeared before congress let alone provided derogatory evidence after she had been cleared. You can read the memo which Trump originally cited as grounds for firing until he admitted he fired Comey for other reasons as well.