Re: NSA, Homeland Security --
Didn't the FBI also agree Russia did the hacking? They just didn't agree on the motive if I recall, which is what most people seem to be arguing about - did they do it to help Trump etc.
Also some of the top cybersecurity companies in the world (CrowdStrike, ThreatConnect, SecureWorks) did their own analysis and came to the same conclusion.
When most of the independent experts come to the same conclusion I tend to side with them.