Mueller tried, couldn't prosecute, which is why this investigation was decided before it even started. They knew there was no collusion, and they knew Comey's firing was justified so there was no obstruction, never mind the fact how could one obstruct the investigation into a crime that wasn't committed, but that flies way over most heads.
You see, the man that gave Mueller all this unchecked authority also penned the memo to fire Comey. They knew there was no collusion, they knew there was no obstruction, yet they still authorized this investigation. There is no doubt in my mind that Manafort was their target all along, and I think Cohen may have been on their radar from the beginning too, although I'm not sure about Cohen. Manafort was the target of this investigation, he's the center of their Trump Insurance
