It would be hard to help Trump if he fired Mueller. Mueller exists because Trump was stupid. Trump should forget about him. Let his lawyers handle it. Trump will just hurt republicans and himself by firing Mueller. He should shut up about it, just don’t make news about it. He should get wins. Last two years, then he can do something about Mueller. Obviously if Mueller had a year and a half with nothing you could just fire the guy.
If Trump wanted to do anything, he should send Mueller after Hillary and the DNC. Mueller should be looking at Russia outside of Trump. I am sure they tried to infiltrate the democrats because they thought that they would control the White House and maybe the Senate. There is no way that Russia did not have a plan for the DNC control.
You certainly raise a valid alternate point. However, Trump just can’t seem to let it go. The only risk to your reasonable suggestion is that Mueller will keep this going, and like the strategic indictment of Casper Weinberger four days before the 1992 presidential election, I predict that if left to his own, Mueller will most certainly spring something unwarranted and nasty to help Democrats right before the 2018 mid-term election, and if left around, will almost certainly drop an October surprise for the 2020 presidential election.
Democrats are nasty. They plot and scheme with a level of malevolence that normal people are not accustomed to, and the corrupt MSM provides enormous air cover allowing them to get away with their dirty work.
Fire Mueller now.