Mueller, Congres and the press have an interest in making the assignment last the duration of Trump's presidency, and causing as much damage as they can, to Trump's administration, friends and family as they can, in the meantime.
Trump and the public have an interest in having an impartial investigation into the bogus allegation completed and reported quickly.
Firing Mueller creates a situation more like keeping the secret investigation alive, with the added bonus that "Trump would not fire Mueller if Trump was innocent."
So the way to keep the investigation short is to limit its scope. Smaller scope, less evidence, easier to report, and so on. We are more than two months into this, and just now finding out that Mueller is going on fishing expeditions. That is the fault of Rosenstein and Mueller, to hide that ball. Call them on it, and let's negotiate the scope of the assignment, IN PUBLIC.
“Mueller is going on fishing expeditions. That is the fault of Rosenstein and Mueller, “
No, that was the plan of Rosenstein and Mueller.