Bob Mueller decided to shoot up the town before he rode off into the sunset.
It is fair enough to observe that in his short but explosive speech, delivered at the Justice Department Wednesday morning, the special counsel did not say anything that wasn’t already set forth in his report — a point being emphasized by the White House. The sprawling report is 448 pages long, however. In his nine-minute address, Mueller quite consciously highlighted the portions of the report that fuel the Democrats’ calls for impeachment.
Mueller was adamant that he did not make a finding on whether President Trump should be charged with obstruction of justice because the Justice Department’s Office of Legal Counsel (OLC) has issued guidance forbidding the indictment of a sitting president. I've argued before that he is completely wrong on this, but that is beside the point.
What matters is that Mueller can be fairly understood to be saying he believed President Trump committed obstruction of justice. That is not the only possible interpretation, but it is the most likely interpretation.
Mueller said Wednesday that if he had concluded there was insufficient evidence to charge Trump with obstruction, he would have said so (as he did with collusion). He then emphasized that he did not say so. That strongly implies that he believes the evidence is sufficient (notwithstanding that the attorney general has found otherwise). Mueller added that, in deciding not to allege obstruction even though the evidence was arguably sufficient to prove guilt beyond a reasonable doubt, he relied on the OLC guidance. Finally, he deduced from this, and from his understanding of the Constitution, that in our system it is for Congress, not federal prosecutors, to deal with presidential misconduct.