“Robert Mueller has a long and sordid history of illicitly targeting innocent people. His many actions are a stain upon the legacy of American jurisprudence. He lacks the judgment and credibility to lead the prosecution of anyone....”
http://www.trevorloudon.com/2018/05/monumental-the-naked-truth-about-robert-mueller/
for your interest...
The general idea is that very possibly Trump, when he and Mueller met the day before Mueller got the job of doing the Witch Hunt, gave Mueller a choice.
It will be made clear soon what has actually been going on behind the scenes.