You have forgotten that the investigation was started in the first place to investigate Russia's role in the 2016 election. The goal was not to go after Trump. Because Mueller had a green light to go wherever his investigation led. I was virtually certain, and I have now been shown to have been correct, that Mueller would discover either or both tax evasion and money laundering involving Russian money, and Trump would be at the center of it . For all we know it may be Mueller's team that also discovered the Foundation fraud and turned it over to Barbara Underwood. In any case, Mueller is smart to get the prosecution distributed in as many venues as feasible. Mueller has the perfect background for an investigation requiring crossing national boundaries. He worked closely with Steele before on the FIFA investigation. He's an old hand at this stuff and knows virtually everyone in the business first hand. I was overjoyed when Rod Rosenstein talked Mueller into heading up the investigation after Trump fired Comey.
The thing that is critically important here is that we understand in depth exactly how the Russian operation worked in detail. Remember this is not an investigation to go after Trump. It is an investigation of how the Russians interfered with the 2016 election. Trump has always operated on the edge between legal and illegal so we shouldn't be surprised if some of trumps illegal activities end up being exposed by the investigation.
The results so far from the Mueller investigation have been nothing short of astounding. Thirty some indictments at least 8 guilt pleas (I think there are a few more actually) Many Russians indicted, details of the hacking operation exposed, etc. Bravo! We have really got more than our money's worth already. Amazing! And the investigation isn't over!.