Mueller is going to be under increasing pressure to demonstrate that he is fair, now that we know that he hid the evidence that Russia's state-owned uranium company was bribing and extorting US uranium truckers from Republican lawmakers back in 2010 when the Obama administration approved a deal to transfer 20% of US uranium production capacity to Russian control. By "hid the evidence," I mean he did not inform other agencies of the existence of the FBI investigation into millions of dollars of Russian kickbacks, bribes, and acts of extortion, even as those other agencies prepared to approve the deal. 

Why did the FBI keep the investigation secret? I don't know. Mueller does. But it MIGHT be because the same Russian uranium interests had already donated over one hundred million dollars to the Clinton enterprises. Revealing the existence of the investigation would inevitably have led back to Hillary