The writer Greg Olear published an excellent piece last Friday (link here) that superbly and thoroughly dissects Barr and why he's so loyal to Trump. The piece is partly titled "The Most Dangerous Man in America."
Trump is surrounded by zealots, true believers, and yes-men, but as Olear makes clear, Barr is in a class by himself. It's like every time he's faced with a choice — the good way or the evil way — he takes the latter.
The linked piece is not long and I highly recommend. Read and share.