In America, you are innocent until proven guilty. That is, unless you are the president and a special investigator is appointed. In that case you are guilty. The only thing that remains is to find which laws you can be prosecuted for. Note: I did not say which crimes you can be convicted of. The difference is that if any crimes are prosecutable, nothing goes to the court.
Instead, it goes to impeachment hearings, where the standard of guilt or innocence is not determined by a jury of your peers. Determining your guilt or innocence then becomes a matter of politics, and not of law. Thus it could result in impeachment. Also note that if Mueller comes up with something that he hopes is impeachable, then he has to convince the House of Representatives to take up impeachment proceedings. In Trump's case, this is harder to do if the House is controlled by Republicans. But if it is controlled by Democrats, then impeachment might be a possibility.
If Trump is ever impeached, that does not mean that Trump needs to leave office, unless the Senate removes him from office. Bill Clinton was actually impeached, but the Senate refused to remove him from Office. But if the Senate did remove Trump from office, that does not mean a do-over of the 2016 election. What it means is that Vice President Pence becomes president. If Pence becomes president, he then has the option of pardoning Trump as Gerald Ford did for Richard Nixon.
In short, Mueller and those who support Mueller, are full of wishful thinking, and have lots of hopes and dreams. I’ll also admit that there is also a very long gravy train feeding Mueller, and his endless cadre of lawyers, prosecutors, and endless staff.