RIP Robert Mueller. However
I have to point out that he knew the details of what was in the report that Barr refused to release. Mueller like many career Justice/Law Enforcement people get bound to honoring the process of things and can lose sight of a higher imperative. That higher imperative is the duty to inform and to warn the public even though you yourself may be in violation of laws, procedures and court decisions and suffer penalties as a result.
What was hidden was obviously very, very bad and would likely have doomed any election hope of the fascist President we now have. I would point out that it is in some ways similar to the parts of the CIA Torture report we were not allowed to see. This country is "We The People" and not "We The Institutions and Agencies of Government" and as such the public must have these kinds of information no matter how bad it casts a shadow on our country or who gets embarrassed and prosecuted.
"We The People" need to demonstrate to the world that as a people we will own up to our wrongs as well as take credit for what we do right. That and that alone is how moral authority is established and held. When the wrongs are hidden from us it inhibits our ability to address the wrongs and by doing so it lessens our moral base.
There are the assistants to Robert Mueller who are alive and know very well what is in the hidden parts of the Mueller Report. I beg them to find the courage to stand up, and if need be sacrifice themselves, and tell us the details of what was hidden. Likewise in the CIA Torture Report.
If they do not the concept of this country as "We The People" may well be in its' last days. Please don't let "We The People" fall to the fascists because you won't fight and provide the information you have. The time is now.