Get it straight. The statements made in the US intelligence report are neither assertions nor known facts. They are an "assessment." This is intelligence double-speak for 'best guess.'

Get this straight as well. It's the head of the intelligence service that makes the final decision on what that best guess is. He's the top guy, and can over-rule the analysts in his own agency if he wants. This is particularly true in any case, such as this, where the heads of the service will not have to answer for what the report says. (All those heads in this case are Obama appointees, and have submitted their resignations.)

Spies lie. Convincingly. It's a big part of their job description. So it's worse than naive to blindly take what they say at face value.