[quadrant]

Here's a classic example of a President inserting himself into a criminal investigation.
In the early 1940’s, the IRS wanted to indict Congressman Lyndon Johnson for criminal income tax evasion. As LBJ was one of the few Deep South Democrats who were fervent New Dealers, FDR intervened and ordered the IRS to drop the indictment and end the investigation.
If that is not presidential interference, I don't know what is.

[Susquehanna Patriot]

in the USA, the DOJ must be responsible to someone ... POTUS, who is elected, and in return is responsble to the voters.

The demonkraps know this, for when they are in charge, not one of them ever demands the DOJ be independent of their party POTUS. The only time the DOJ or any agency is ever independent of the POTUS is when they get commit crimes on their party’s POTUS, then all of a sudden, 11th hour emails are written about how POTUS told everyone present to do everything by the book.