Not at all. The people who are being arrested, or charged, at least by Mueller, have been directly linked to Russia.
Flynn lied about secret discussions he had with a Russian ambassador about Obama's sanctions.
Papadopoulos lied about talking to a Russian agent about getting dirty info about Hillary.
Manafort was charged with financial crimes, all of which were related in various forms to taking money from Putin backed Ukrainian oligarchs.
Mueller's not asking these guys about Trump's prowess in the sack. It's all related to Russia.
Once you get to Cohen, Pecker, Weisselberg etc, those cases are being handled by SDNY and the Manhattan DA, not Mueller. If any of those people have info about Trump/Russia, which is already alleged to be the case with Cohen for sure, then they'll be referred to Mueller.
When other crimes are discovered during the investigation process, do you think they should just be ignored because they're not directly linked to Russia?
Just as a refresher, Whitewater started as an investigation into a shady Clinton real estate deal and when Starr couldn't find anything after four years, he lucked into a blue dress with a come stain and called for impeachment.