Speculation would be to the why. --You've no clue. You think you do, but you don't. You know next to nothing about this whole goosechase.
That's possibly true as long as he is President anyway. It's more or less an open question since no one has tried to convene a Grand Jury with the intention of indicting a sitting President -- No one yet anyway. And the Constitution is silent on this matter. The Constitution says the President can be impeached for high crimes and misdemeanors. But it doesn't say they can't be indicted. Legal scholars have opined that the remedy stated in the Constitution was intended to replace indictment of a sitting President, but other legal scholars have opined that impeachment is a political remedy to be used to get rid of a President, but is an action entirely apart from indictment for a specific crime, even the same crime he/she may have been impeached for. The Court has never weighed in on this question. In any case, it has been assumed, and seems to be the general consensus among legal scholars, that impeachment and removal from office does not impart immunity from prosecution. Bummer, if you're Donald Trump.
Nobody cares about narratives other than cultists who wanna ignore reality. Reality defines narratives, not vice versa.
A sitting president can only be judged by the house and senate. He/she can be prosecuted after leaving office. --But it would never happen. He/she would be pardoned by their successor to spare the country. --The president is above the law.
Speaking of narratives, actual top story on Breitbart right now: EXCLUSIVE—How Melania’s Upbringing in Communist Eastern Europe Shaped Her Fight for Freedom in America