There exists a long history regarding Muller's checkered past. The following three related links are but three of a plethora on the matter.
The 8 dirtiest scandals of Robert Mueller no one is talking about
As he investigates Trump's aides, Robert Mueller's record shows surprising flaws
Robert Mueller’s Sordid History Of Illicitly Targeting Innocent People
Here is a latest possible connection
"Mueller-Connected Boston Mobster Whitey Bulger Killed in Prison… As He Was About to Out FBI Officials"
Mueller's list of iniquities continues to grow.