Do the intelligence agencies actually agree on this as unanimously as you're saying? Here's a quote from the testimony of James Clapper on Russia/Wikileaks connection:
That was from a month and a half ago. It seems more likely that he's changed his mind or seen new information than that the DHS and FBI are putting out joint press releases that contradict the beliefs of the DNI, but who knows, maybe the DHS/FBI leadership is involved in some kind of squabble with Clapper or something....?