Mueller, by his own actions, and his choice of “investigators” have delegitimized himself, and his witch hunt.
If you look at the dueling investigations as a battle between team Trump and the Deep State, here is how it is set out:
Team Trump: Congress and the IG, Horowitz, have uncovered and continue uncover unprecedented abuses by the DOJ/FBI and State Dept. The facts are undeniable but the media denies them anyway. There is no one in a position actually prosecute the criminals.
Deep State: Mueller is positioned and willing to prosecute. An inconvenient circumstance for him is that he has no facts to support such a prosecution. But he is willing to create a set of facts, if at all possible, to support an obstruction charge. Admittedly, such a prosecution or recommendation for impeachment might look petty given the avalanche of facts uncovered by Team Trump.
What probably happens: a truce. No real reform and no significant prosecutions, certainly not by Team Trump. (Deep State will probably back off sentencing Flynn since inconvenient facts would be exposed at trial).