It is frustrating to see Trump seeming to get away with what he has done but you can't be jumping into the lack of logic and reasoning that the right frolics in.

Mueller does not have the authority to do anything. He was appointed to investigate conspiracy to interfere with the election. He found substantial evidence of interference but did not have sufficient evidence to meet the burden of proof for conspiracy by Trump or his people. The evidence just wasn't there within the parameters of the investigation.

He did find evidence of obstruction but felt he could not indict Trump because of the OLC policy. You can question that policy but again, it wasn't Mueller's decision to make.

Did you believe that mash up of Trump running and Mueller catching him and throwing him on the hood of the car? That is not how this works. Mueller gave his report to his superior and unfortunately his superior is a political hack with no loyalty to the country. That isn't Mueller's fault either.

Finally, Treason is an actual thing that has a specific meaning. Did Trump betray the country? Likely, yes. That is petty treason, a strictly non-legal term. Did he make war on the US or offer aid and comfort to an enemy? Not within the scope of the election investigation.