How does that make any sense? The whole point of having a president is that he is a civilian who is still subject to US laws (vs a King who is unaccountable). The ENTIRE reason the US exists is because prior governments did not hold their leaders accountable.
How can you possibly argue that Trump is some sort of unaccountable and un-indictable leader (a king) when the constitution specifically states that he is not? Does Mueller believe Trump is King?
Where does it state that, specifically?