To me that's comment is not correct.
Original quote from Rod Rosenstein's statement on hiring Mueller:
"The letter announcing the appointment says that Mueller is authorized to investigate "any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; and...any matters that arose or may arise directly from the investigation."
Looking at Trump's business dealings through his years as a businessman is not within the scope or parameters of his assigned investigation.
The last special prosecutor knew from the outset that Richard Armitage was the leaker of Valerie Plame and yet continued until he trapped Scooter Libby.
Mueller doesn’t care what they had in mind when they hired him.
Normal people wouldn't think so but to a lawyer "any matters that arose or may arise directly from the investigation" is a hole that a Mack truck will fit comfortably through.
You are absolutely correct. Rosenstein has taken a hands off approach to this thing but he created this monster, he has to rein it in.
Also I want to know what this thing is costing us. How do we find out?
Precisely