Hindsight shows that Mueller has used Williams to withhold evidence from other grand juries beforeRuby Ridge (1992), Waco (1993), World Trade Center (1993), Oklahoma City Bombing (1995), 9/11 (2001) and now the Trump-Russia Hoax.
Mueller himself argued this case before the Supreme Court, along with his buddy and fellow deep-stater, Kenneth Starr. It's a completely rigged system and has been for quite some time.
Kenneth Starr blocked Miguel Rodriguez in 1994 from investigating the death of Vince Foster as a murder tied to the Clintons; Rodriguez outlined his reasons in his letter of resignation.