The Muller Report explicitly asked Congress to investigate further. Muller stated that Justice Department policy tied his hands to look any further into a sitting President.
Barr then gets ahead of it saying “this is a nothingburger”. That becomes the media narrative before anyone outside the Justice Department can actually read it. One which you’re now repeating. Impeachment isn’t like a court case; it is primarily a political process. Barr knew this, and to this day, Trump had no clue how much Barr saved his ass.
Read the Muller Report, not the headlines. It is a damning document.