To further pile on against such naivete as, "But Mueller hasn't shown evidence of Collusion, so there must have been none."
Mueller runs a tight, leakless ship. We see where he is only when indictments come down. He's several steps ahead of us grasping ignorants in the peanut gallery. Only when a *complete*, unassailable case against Trump is put together will we see it.
The *political* concerns here are potent. A slavering, spineless GOP Majority will steadfastly support Trump as long as the Base of Deplorables does not desert their Dear Leader. In such an environment, it behooves Mueller to really and truly get all his ducks in a row before moving. Indeed, waiting for support in the Base to at least waver is in the best interest of Justice. Otherwise those so called GOP "Lawmakers" will do their best to downplay and ignore any evidence so as to retain their power/position.
In this environment, the mindless Base holds the power because upon it the politicos' positions depend. The latter are in the thrall of the former because they fear being primaried above all. Personal power comes before country, and slavish toeing to the Trumpian line is the route by which to keep it.
It is truly to be naive to expect the normal course of Justice to proceed where this President is concerned.