Well, I am a little surprised by the result. I have a few lingering questions about it, like why Mueller, if he thought the obstruction case was ambiguous and had at least some incriminating evidence, did not attempt to interview Trump to at least probe about intent, especially when he admitted at least once in a television interview that he dismissed Comey because of the ongoing Russia investigation.
It could be a constitutional question that made him hesitate. What we read was the result of Mueller punting the decision to Barr/Rosenstein, and the decision was predictable.
I'm no lawyer, so that is of course possible. But on the face of it, while there is a lingering Constitutional ambiguity regarding whether a sitting president can be indicted, I know of no legal ambiguity in calling a president in for questioning under oath in a federal investigation of activities of his own campaign. If there is no such legal ambiguity, the decision not to interview Trump was Mueller's call, and it would be nice to know what his basis was for making it. I completely agree that punting the decision to pursue an obstruction case to Barr left the result predictable.