My very quick take on the Barr letter and CNN reportage
The Live CNN Commentary is potentially misleading, although as I'm writing this, there is some improvement. Various commentators are focusing on whether there was sufficient evidence on obstruction to establish guilt beyond a reasonable doubt, and so they are drawing the distinction between an impeachment, which is political, and a criminal prosecution, which is obviously legal. But this misreads the letter.
The letter does not say that Mueller declined to make a judgment because he did not believe the evidence could satisfy the beyond a reasonable doubt standard on obstruction. Instead the letter says that Mueller elected not to make a judgment on that, full stop, and instead to report the facts, adding that the report result neither incriminates nor exonerates on that specific question.
This means that Mueller made the judgment that other institutional actors should make the decision on how to assess the data on obstruction that he reported, not that the standard of proof in a criminal proceeding could not be met. It is Barr that said he believed the criminal standard could not be met, not Mueller. William Barr, in consultation with Rod Rosenstein, decided that that they did not have the evidence to pursue this criminally, but of course Barr is answerable to Trump. For those hoping this would bring down Trump, I am not being Pollyannaish, but I am saying that the live commentary is too soon, and potentially misleading based on what the actual letter says.
Bottom line: Mueller did not conclude that the criminal standard could not be met; he decided that other institutional actors should make that assessment based on the data he reported. Barr made an independent determination not to pursue criminal action.
Separately, the letter does offer direct evidence from the Mueller report, in the form of a quotation, showing that Trump and his advisors did not engage in what is loosely being called collusion.