A central figure in his 2016 election interference investigation is a bar-fighting brawler with criminal ties to the Russian mafia. 

The special counsel inexplicably failed to mention this.

The Intercept reports:

THE REDACTED VERSION of special counsel Robert Mueller's report contained quite a bit of information about the perfidy of the Trump White House, the lack of evidence on collusion, and the limits of testimony to support a criminal charge of obstruction. But what's most interesting is what the report did not say.

...

The most glaring omission concerns Felix Sater. The report describes Sater as a "New York-based real estate advisor," which is technically accurate — but a bit like calling O.J. Simpson a "California-based football player."