@katrinakatrinka yes, we could spend all day picking and choosing our preferred experts to echo our sides, but we don't need to since we can see for ourselves what's laid out plain to see.
How many branches are there in the US government? Surely we can agree that there are three, right?
Well, with only three branches, legislative, executive, and judicial, there is no room for a fourth branch for the DOJ.
Therefore, the DOJ must be acting on authority of the president, in whom all executive power is vested.
We could change this and add a fourth branch if we'd like, but so far, that's the fundamental design of the US government.