As has been discussed multiple times, collusion in and of itself is NOT a crime.
The sad thing is, no collusion has been proven to have even happened.
What has been proven (and won't even be investigated) is unprecedented domestic spying which is abuse of power by Obama. What has been proven are laws broken by Hillary Clinton with classified emails and using a fictional dossier to generate a a FISA warrant to justify its abuse of power.
The evidence has already been laid out in a slam dunk case for how Clinton committed multiple felonies by violating the espionage act.
What is even more astounding is how this is ignored and excused by those on the left, through their donkey tinted glasses. Defending the indefensible simply because they are on "your team".
I digress, but it was telling that The Clintons - who used to command hundreds of thousands of dollars per speech to their foundation when they had power and could pay to play were just in Montreal and got less fans than the hapless Haps even get by filling only 17% of the available seating - and most tickets sold at a steep discount of $10.
By most accounts the Mueller investigation is winding down, even from comments they have made, and what are the results? So far, negligible. No collusion has been identified or proven (primarily because they refused to look at those who actually were guilty of it)
All criminal indictments to date are process crimes or financial crimes, either committed well before the people interacted with Trump, or AFTER the investigation began, and created by the investigation
Other than the point that this investigation is completely political, a "successful" independent investigation doesn't require indictments to be successful. Exonerating everyone involved is just as successful - if it weren't politically motivated.